Search

Resumen Introduccion La medicion de la presion arterial (PA) en la consulta es un procedimiento recomendado, aunque, actualmente, se esta generalizando el uso de las medidas ambulatorias. Objetivo Conocer el grado de control de la hipertension arterial (HTA), usando la medicion en la clinica. Material y metodos Durante noviembre del 2019, se recogieron datos demograficos, clinicos, la PA sistolica (PAS) y diastolica (PAD) en consulta con observador, usando un aparato automatico con lectura diferida y datos de monitorizacion ambulatoria de la PA (MAPA) en caso de haberse realizado. Resultados Se incluyeron 102 pacientes (67 varones), con edad media de 64,9 anos, 30% diabeticos y 34% con complicaciones cardiovasculares. Un 70% tenian una PA clinica controlada ( Conclusion El uso de aparatos automaticos disminuye el fenomeno de bata blanca mejorando el porcentaje de pacientes con HTA controlada en la consulta. Sin embargo, este control no se confirma fuera de ella, lo que evidencia la importancia de la MAPA en la evaluacion global de la HTA. La toma de la PA en la consulta es util en la valoracion inicial del paciente y aporta aspectos educativos, aunque hay que optimizar la metodologia para definir su papel en la clinica.

More than two thirds of people over 65 are hypertensive. Along with the high prevalence, hypertension is associated by comorbidities that originates a heterogeneous elderly population in relation to their autonomy and functional capacity. At this age, hypertension has special characteristics that make its management difficult, highlighting by isolated systolic hypertension due to the vascular stiffness typical of aging. Although decision-making is based on the clinical measurement of blood pressure, it is known that in the elderly pressure is subject to numerous influences: temporal (absence of night dipping), of the environment (exacerbation of the white coat phenomenon) and of the position (orthostatic hypotension). These circumstances must be taken into account when evaluating and deciding on therapy. At this age, there is sufficient evidence that treatment reduces both cardiovascular morbimortality and all-cause mortality.

Supplemental Digital Content is available in the text., Background. Long-term cardiovascular (CV) events are a frequent cause of death and disability after liver transplant (LT). Although a more in-depth, risk-adapted control of CV risk factors may result in improved post-LT CV outcomes, an accurate stratification of the CV risk of LT recipients to better implement preventive strategies is lacking. Aortic pulse wave velocity (aPWV) is a surrogate of arterial stiffness that has been suggested as a biomarker of CV risk; it has never been evaluated in adult LT recipients. Methods. In a single-center prospective study, we included 122 LT recipients at 12 (n = 39), 60 (n = 45), or 120 (n = 38) mo after LT. aPWV estimation by oscillometry, clinical assessment of CV risk factors, and CV risk estimation by standard clinical scores (systematic coronary risk evaluation and pooled cohort equation) were performed. The incidence of CV events during prospective follow-up was registered. Results. aPWV was independently associated with age and the grade of control of blood pressure. After a median follow-up of 35 mo, 15 patients (12%) presented a CV event. Higher aPWV, diabetes, past or present smoking habit, previous CV events, lower eGFR, being in systematic coronary risk evaluation or pooled cohort equation high-risk groups, and higher levels of total cholesterol, LDL-cholesterol, creatinine, and triglycerides were associated with the incidence of CV events at univariate analysis; aPWV, past or present smoking habit, and triglycerides were independent predictors of CV events. Conclusions. According to our results, aPWV mirrors CV risk in LT recipients and thus may be a useful CV risk biomarker in this population. Considering these preliminary results, its accuracy in stratifying risk requires confirmation in further studies.

Abundant evidence from epidemiological and experimental studies has established a link between salt and blood pressure. However, there is heterogeneity in the blood pressure responses of humans to changes in sodium intake. Those individuals in whom a severe, abrupt change in salt intake causes the least change in arterial pressure and are termed salt-resistant, whereas in those in whom this leads to large changes in blood pressure, are called salt sensitive. Classically, Guyton's theory of the pressure-natriuresis phenomenon has been accepted to explain the pressor effect of salt, as well as the fundamental role played by the different protein sodium transporters of the renal tubules. In recent years, new theories have emerged pointing to the possible role of the immune system and the existence of a third sodium store in the body as aetiopathogenic factors.

A 31-year-old woman presented at the emergency room after experiencing colic pain in the right iliac fossa for 5 days. She had previously consulted another center, where deterioration of renal function had been identified and abdominal computed tomography (CT) angiography had shown a dissection of the right renal artery, with areas suggestive of infarction in the right kidney, as well as an aneurysm in the left renal artery and a smaller left kidney. The patient had no relevant family or personal history except posttraumatic carotid-cavernous fistula in 2014, which had been treated with embolization. In our hospital, the patient was hypertensive and acute renal failure was confirmed, accompanied by an increase in lactate dehydrogenase and isomorphic microhematuria. After a new CT Scan, in addition to the lesions described in the renal arteries, another aneurysm in the splenic artery and an aneurysm of the right femoral artery were identified. Antihypertensive treatment was initiated with calcium antagonists and anticoagulation. Subsequent renal arteriography confirmed the dissection of the right renal artery, which could not be repaired, and a coated stent was placed in the left renal artery to exclude the aneurysm. The splenic artery lesion was treated 2 months later. The etiological diagnosis in this young woman was challenging. The presence of visceral aneurysms suggested a differential diagnosis comprising fibromuscular dysplasia, vasculitis, and collagenopathies. Using a multidisciplinary approach and directed anamnesis, the presence of frequent sprains, joint hypermobility, and skin fragility was confirmed. Blood immunology and CT angiography including the thoracic and cervical territories were normal. Echocardiography revealed tricuspid insufficiency. All these data suggested the presence of a collagen-like Ehlers-Danlos syndrome (vascular form). The diagnosis was confirmed by the genetic study, which showed a pathogenic mutation in the COL3A1 gene. Currently, the patient is asymptomatic with recovered renal function following treatment with a beta-blocker and antiplatelet therapy.

BACKGROUND Central blood pressure (BP) is considered as a better estimator of hypertension-associated risks than peripheral BP. We aimed to evaluate the association of 24-hour central BP, in comparison with 24-hour peripheral BP, with the presence of left ventricular hypertrophy (LVH), or diastolic dysfunction (DD). METHODS The cross-sectional study consisted of 208 hypertensive patients, aged 57 ± 12 years, of which 34% were women. Office and 24-hour central and peripheral BP were measured by the oscillometric Mobil-O-Graph device. We performed echocardiography–Doppler measurements to calculate LVH and DD, defined as left atrium volume ≥34 ml/m2 or septal e′ velocity RESULTS Seventy-seven patients (37%) had LVH, and 110 patients (58%) had DD. Systolic and pulse BP estimates (office, 24-hour, daytime, and nighttime) were associated with the presence of LVH or DD, after adjustment for age, gender, and antihypertensive treatment, with higher odds ratios for ambulatory-derived values. The comparison between central and peripheral BP estimates did not reveal a statistically significant superiority of the former neither in multiple regression models with simultaneous adjustments nor in the comparison of areas under receiver-operating curves. Correlation coefficients of BP estimates with left ventricular mass, although numerically higher for central BP, did not significantly differ between central and peripheral BP. CONCLUSIONS We have not found a significant better association of 24-hour central over peripheral BP, with hypertensive cardiac alterations, although due to the sample size, these results require further confirmation in order to assess the possible role of routine 24-hour central BP measurement.

We aimed to evaluate the association of aortic and brachial short-term blood pressure variability (BPV) with the presence of target organ damage (TOD) in hypertensive patients. One-hundred seventy-eight patients, aged 57 +/- 12years, 33% women were studied. TOD was defined by the presence of left ventricular hypertrophy on echocardiogram, microalbuminuria, reduced glomerular filtration rate, or increased aortic pulse wave velocity. Aortic and brachial BPV was assessed by 24-hour ambulatory BP monitoring (Mobil-O-Graph). TOD was present in 92 patients (51.7%). Compared to those without evidence of TOD, they had increased night-to-day ratios of systolic and diastolic BP (both aortic and brachial) and heart rate. They also had significant increased systolic BPV, as measured by both aortic and brachial daytime and 24-hours standard deviations and coefficients of variation, as well as for average real variability. Circadian patterns and short-term variability measures were very similar for aortic and brachial BP. We conclude that BPV is increased in hypertensive-related TOD. Aortic BPV does not add relevant information in comparison to brachial BPV.

Background/Aims: Cyclosporine (CsA) is a calcineurin inhibitor widely used as an immunosuppressant in organ transplantation. Previous studies demonstrated the relationship between CsA and renal sodium transporters such as the Na-K-2Cl cotransporter in the loop of Henle (NKCC2). Experimental models of CsA-induced hypertension have shown an increase in renal NKCC2. Methods: Using immunoblotting of urinary exosomes, we investigated in CsA-treated kidney transplant patients (n = 39) the excretion of NKCC2 and Na-Cl cotransporter (NCC) and its association with blood pressure (BP) level. We included 8 non-CsA-treated kidney transplant patients as a control group. Clinical data, immunosuppression and hypertension treatments, blood and 24-hour urine tests, and 24-hour ambulatory BP monitoring were recorded. Results: CsA-treated patients tended to excrete a higher amount of NKCC2 than non-CsA-treated patients (mean ± SD, 175 ± 98 DU and 90 ± 70.3 DU, respectively; p = 0.05) and showed higher BP values (24-hour systolic BP 138 ± 17 mm Hg and 112 ± 12 mm Hg, p = 0.003; 24-hour diastolic BP, 83.8 ± 9.8 mm Hg and 72.4 ± 5.2 mm Hg, p = 0.015, respectively). Within the CsA-treated group, there was no correlation between either NKCC2 or NCC excretion and BP levels. This was confirmed by a further analysis including potential confounding factors. On the other hand, a significant positive correlation was observed between CsA blood levels and the excretion of NKCC2 and NCC. Conclusion: Overall, these results support the hypothesis that CsA induces an increase in NKCC2 and NCC in urinary exosomes of renal transplant patients. The fact that the increase in sodium transporters in urine did not correlate with the BP level suggests that in kidney transplant patients, other mechanisms could be implicated in CsA-induced hypertension.

Background and aim Central blood pressure (BP) is increasingly considered as a better estimator of hypertension associated risks. We aimed to evaluate the association of 24-h central BP, in comparison with 24-h peripheral BP, with the presence of target organ damage (TOD). Methods Cross-sectional study of 208 hypertensive patients, aged 57 ± 12 years, 34% women. Office (mean of 4 measurements) and 24-h central and peripheral BP were measured by the oscillometric Mobil-O-Graph device. TOD was assessed at cardiac (left ventricular hypertrophy by echocardiography), renal (reduction of glomerular filtration rate and/or microalbuminuria), and arterial (increased aortic pulse wave velocity) levels. Results A total of 107 patients (51.4%) had TOD (77, 35% patients left ventricular hypertrophy; 54, 25.9% renal abnormalities; and 40, 19.2% arterial stiffness). All SBP and pulse BP estimates (office, 24-h, daytime, and night-time) were associated with the presence of TOD, after adjustment for age, sex, and antihypertensive treatment, with higher odds ratios for ambulatory-derived values. Odds ratios for central and peripheral BP were similar for all office, 24-h, daytime, and night-time BP. After simultaneous adjustment, peripheral, but not central, 24-h and night-time SBP and pulse pressures were associated with the presence of TOD. Conclusion TOD in hypertension is associated with BP elevation, independently of the type of measurement (office or ambulatory, central or peripheral). Central BP, even monitored during 24 h, is not better associated with TOD than peripheral BP. These results do not support a routine measurement of 24-h central BP.

Background/Aims Height-adjusted total kidney volume (htTKV) is the best marker of disease progression in early autosomal dominant polycystic kidney disease (ADPKD) when renal function still remains normal. The usefulness of cystatin-C as a biomarker to assess renal function according to renal volume has not been studied in ADPKD patients. Methods Observational and cross-sectional study of 62 ADPKD patients. htTKV, creatinine and cystatin-C estimated glomerular filtration rate (eGFR) were determined. Correlations between htTKV and eGFR were studied. A control group was used to determine the association between renal function differences and htTKV. Results htTKV significantly correlated with cystatin-C-eGFR (r = -0.384, p = 0.002) but not with creatinine- eGFR (r = -0.225, p = 0.078). With htTKV stratified into tertiles, a significant difference of cystatin-C-eGFR but not in creatinine-eGFR was detected in the third tertile when compared with the first tertile group (110.0 +/- 22.2 vs 121.3 +/- 7.2; p = 0.023 and 101.8 +/- 17.2 vs 106.9 +/- 15.1; p = 0.327 respectively). When cystatin-C-eGFR of the controls was used as the reference, htTKV above 605 ml/m identified with a 75% sensitivity and 84.9% specificity those patients with a significant worse kidney function. However, this cut-off value could not be identified using creatinine-eGFR. Conclusions Cystatin-C-eGFR but not creatinine-eGFR correlated with htTKV in ADPKD patients in early stages of the disease. Differences in cystatin-C-eGFR but not in creatinine-eGFR have been identified through htTKV tertiles. A htTKV above 605 ml/m is associated with a worse renal function only if cystatin-C-eGFR is used. Cystatin-C-eGFR should be studied in prospective studies of early stages of ADPKD to determine its usefulness as an early marker of disease progression.

It has been suggested that aortic BP could be a better predictor of target organ damage (TOD) than peripheral BP. However, studies examining such relationship by using ABPM are scarce. We aimed to examine such relationship in a cohort of hypertensive patients. A total of 208 patients (34% women; mean age: 57±12 years, 90% on antihypertensive treatment) were recruited from 4 hospital clinics in the area of Barcelona, Spain. The presence of TOD was determined if one of the following were present: cardiac, defined as the presence of LVH (LVMI ≥ 115 g/m 2 in men or ≥ 95 g/m 2 in women); renal, defined as the presence of either albuminuria (UAE ≥ 30mg/g) or reduced eGFR (< 60 ml/min/1.73 m 2 , by CKD-EPI formula), or both; vascular: aortic PWV ≥ 10 m/s. Clinic (mean of 4 measurements) and 24-h brachial and aortic BP were determined by the use of the portable automated Mobil-O-Graph device. LVH was present in 37%, albuminuria (17%), reduced eGFR (14%), or both were present in 26%, and elevated aortic PWV in 18%. Overall, 51% of patients presented TOD in at least one organ, whereas 6.3% have all renal, cardiac, and vascular alterations. After adjustments for age, gender, and the use of antihypertensive treatment, odds ratios for clinic, 24-hour, daytime, and nighttime brachial and aortic SBP and pulse pressure (PP) were all significantly associated with the presence of TOD. Higher odds ratios were observed for PP, compared to SBP, and for 24-hour estimates, compared to clinic, daytime or nighttime values. The OR for 5 mmHg increase in brachial and aortic PP were respectively 1.38 (1.16-1.60) and 1.41 (1.14-1.70). PP amplification or augmentation index (clinic or 24-h-derived) were not significantly associated with the presence of TOD, after adjustments. Considering specific organ alterations, aortic SBP and PP estimates were associated with LVH and aortic PWV, but not with albuminuria or reduced eGFR. Both aortic SBP and PP are associated with the presence of TOD in hypertensive patients. The association is stronger for 24-h PP and for LVH and arterial stiffness, whereas renal alterations show a weaker association. The use of ABPM including aortic BP measurement can be of interest in predicting cardiovascular alterations in hypertension.

Resumen El gran desarrollo tecnologico en la era de la posgenomica esta condicionando un cambio de rumbo de la investigacion pasando de una investigacion de moleculas individuales («reduccionista») a una investigacion de conjunto e integracion en sistemas dinamicos, lo que actualmente se denomina biologia de sistemas. Una de las areas que esta sufriendo mas cambios ha sido la investigacion de las proteinas, lo que ha condicionado la aparicion de una nueva disciplina denominada proteomica. En este articulo de revision se pretende, de una manera sencilla, introducir a los clinicos en la proteomica y en las nuevas tecnologias que se utilizan para el estudio de las proteinas y revisar los trabajos mas relevantes que han aplicado esta tecnologia al estudio de las enfermedades cardiovasculares.

Abundant evidence from epidemiological and experimental studies has established a link between salt and blood pressure values. Individuals have different grades of susceptibility to the pressure effect of salt, a phenomenon known as salt sensitivity. The phenomenon of increase or no change in BP blood pressure values when changing from a low-salt diet to a high-salt diet has resulted in a concept called salt sensitivity or resistance. Salt sensitivity increases with age, black race, diabetes mellitus and renal diseases. A variety of different techniques have been used to assess blood pressure response to changes in salt intake in humans. However, due to the complexity of the procedure they are mainly used for research and occasionally for clinical practice.

Fabry disease is an X-linked recessive inborn error of glycosphingolipid metabolism caused by the deficient activity of the lysosomal enzyme, alpha-galactosidase A. Enzyme replacement therapy (ERT) for this disorder has been available in Europe since 2001. However, its effect on advanced renal failure remains controversial. We report the case of a patient whose decline in renal function was reduced by the administration of ERT (agalsidase-alpha). This reduction was more pronounced after doubling the dose of the enzyme. The rate of deterioration of eGFR went from 6.3 ml/min/year prior to the start of ERT (0.2 mg/kg) to 2 ml/min/year (0.4 mg/kg). To our knowledge, this is the first reported case of a patient with moderately impaired renal function treated with high doses of ERT and follow-up of 6 years. The data shown here suggest that ERT may have a very positive impact on renal function even in advanced stages. The role of proteinuria and its control seem to have a clear responsibility for this favorable outcome.

Es clasica la asociacion de la proteinuria con la enfermedadrenal. De hecho, hasta no hace mucho, la proteinuria solose consideraba como el resultado de la enfermedad renalque produce un defecto en la barrera de filtracion que per-mitiria el paso de moleculas de mayor tamano. Actualmen-te, este concepto se ha ampliado de forma notable, y la pro-teinuria ha pasado a ser no solo marcador de enfermedadrenal, sino que se ha indicado su papel como mediador, oincluso como causa de progresion de la nefropatia. Asimis-mo, la proteinuria se considera hoy un marcador de eficaciaterapeutica renoprotectora del tratamiento con inhibidoresdel sistema renina-angiotensina (SRA).Mas alla del area nefrologica, se ha descrito, y tambien revi-sado en editoriales anteriores de esta revista, que no solo laproteinuria, sino pequenas cantidades de albumina urinaria(microalbuminuria), son marcadores sensibles de enferme-dad cardiovascular (ECV)

En la reabsorcion tubular de sodio y agua estan implicados los transportadores renales de sodio y los canales de agua o aquaporinas, que se localizan en las membranas apicales y basolaterales de las celulas epiteliales a lo largo de los tubulos renales. Los principales transportadores de sodio y canales de agua apicales situados a lo largo de la nefrona son: el intercambiador sodio-protones tipo 3 (NHE-3), que reabsorbe la mayoria del sodio procedente del filtrado glomerular, el cotransportador sodio-fosfato tipo II (NaPiII) y la aquaporina-1, todos ellos localizados en el tubulo proximal; el cotransportador de sodiopotasio-2 cloros (NKCC2), clave en la reabsorcion de sodio en la rama gruesa del asa de Henle; el cotransportador sodio-cloro (NCC) en el tubulo distal y el canal epitelial de sodio (ENaC) y la aquaporina-2, ubicados en el tubulo colector. Hay varios estudios experimentales en los que se ha puesto de manifiesto el papel de estas proteinas en determinadas enfermedades asociadas a trastornos en el balance hidrosalino. En humanos, la orina es la fuente ideal para la obtencion no invasiva de biomarcadores utiles en el diagnostico y el seguimiento de enfermedades renales. Asi, proteinas de localizacion apical, como algunos transportadores renales de sodio o aquaporinas que se excretan a la luz tubular, pueden detectarse en orina y podrian resultar biomarcadores de determinados trastornos en el balance hidrosalino. En la actualidad se esta realizando numerosos trabajos en patologia humana para definir mejor el papel de estas proteinas en la clinica. Palabras clave: Biomarcadores urinarios. Aquaporina-2. Reabsorcion tubular. Sodium transporters and aquaporins: future renal biomarkers? Renal sodium and water reabsorption is mediated by renal sodium transporters and water channels or aquaporins which are localized in the apical and basolateral membranes of tubular epithelial cells. The main apical sodium transporters and water channels located along the nephron are: sodium-proton exchanger subtype 3 (NHE-3) which reabsorbs most of the sodium coming from the glomerular filtrate, sodium-phosphate type II cotransporter (NaPiII) and aquaporin-1, all of which are located in the proximal tubule; sodium-potassium-2 chloride cotransporter (NKCC2) which plays a key role in sodium reabsorption in the thick ascending limb; the sodium-chloride cotransporter (NCC) in the distal tubule; and the epithelial sodium channel (ENaC) and aquaporin-2 located in the collecting tubule. There are some experimental studies in which the role of these proteins has been associated with the pathophysiology of several sodium and water balance disorders. In humans, urine is the perfect source to obtain biomarkers useful for the diagnosis of kidney diseases and the assessment of disease progression without the use of invasive procedures. Thus, some of the renal sodium transporters or the aquaporins located in the apical membrane which are excreted in the tubular lumen and detected in urine could become biomarkers of some sodium and water balance disorders. Nowadays there are many studies investigating the role of these proteins in humans in clinical settings.

Dysregulation of renal aquaporins and Na-Cl cotransporter in Hepatic cirrhosis is associated with defective regula- CCl4-induced cirrhosis. tion of water balance. At initial stages of decompensated Background. Severe hepatic cirrhosis is associated with ab- cirrhosis, water retention by the kidney is initially isos- normal renal water retention. motic and is thought to be secondary to excessive stimu- Methods. Semiquantitative immunoblotting was employed lation of renal tubule salt absorption. At least part of to investigate the abundance of the major renal aquaporins (water channels) and sodium-dependent cotransporters in kid- this isosmotic water retention is thought to be associated neys from control rats and rats with cirrhosis secondary to with a marked increase in proximal tubule fluid absorp- chronic CCl4 inhalation. tion documented by micropuncture studies in animal Results. The cirrhotic rats had ascites and manifested a water models (1, 2) and lithium clearance measurements in excretion defect detected by a standard water-loading test. cirrhotic patients (3, 4). With more severe hepatic cirrho- The abundance of aquaporin-1 (the major aquaporin in the proximal tubule) was increased, an effect markedly accentu- sis, free water retention can occur in excess of NaCl ated in high-density membrane fractions prepared by differen- retention leading to dilution of the extracellular fluid. tial centrifugation. Differential centrifugation studies demon- Excess free water retention presumably involves modu- strated a redistribution of aquaporin-2 from high-density to lation of water transport beyond the proximal tubule. low-density membranes, compatible with increased trafficking Both phases of water retention are reproduced in animal of aquaporin-2 to the plasma membrane. The abundance of aquaporin-3, but not aquaporin-2, was increased in collecting models of hepatic cirrhosis, including a model of cirrhosis ducts of rats with CCl4-induced cirrhosis. The Na-K-2Cl co- induced by repetitive CCl4 inhalation (5). In the present transporter of the thick ascending limb showed no change in study, we use the CCl4-inhalation model of hepatic cir- abundance. However, the abundance of the thiazide-sensitive rhosis to investigate the molecular basis of the water Na-Cl cotransporter of the distal convoluted tubule was mark- excretion abnormalities seen in hepatic cirrhosis. edly suppressed in cirrhotic rats, possibly contributing to a defect in urinary dilution. Physiological studies in aquaporin knockout mice (6, 7) Conclusions. In this model of cirrhosis, the development of and studies of patients with mutations of the aquaporin-2 a defect in urinary dilution may be multifactorial, with contribu- water channel (8) have made it clear that the major tions from at least four abnormalities in transporter regulation: fraction of water transport across renal tubule epithelia (1) an increase in the renal abundance of aquaporin-1, (2 )a is mediated by aquaporins. Thus, the abundance of indi- cellular redistribution of aquaporin-2 in the collecting duct vidual aquaporins in the plasma membranes of renal compatible with trafficking to the plasma membrane without an increase in total cellular aquaporin-2, (3) an increase in the epithelial cells is believed to be the major determinant renal abundance of aquaporin-3, and (4) a decrease in the of epithelial water permeability. Aquaporins are ex- abundance of the thiazide-sensitive cotransporter of the distal pressed in three main sites in the kidney, namely, the convoluted tubule. proximal tubule, the descending limb of Henle's loop, and the collecting duct (9). Aquaporin abundance at these sites can be readily assessed by quantitative immu

We examined the effect of temporary renal ischemia (30 min or 60 min) and reperfusion (1 day or 5 days) on the expression of renal aquaporins (AQPs) and urinary concentration in rats with bilateral ischemia-induced acute renal failure (ARF). Next, we tested whether reducing ischemia/reperfusion (I/R) injury by treatment with α-melanocyte stimulating hormone (α-MSH) affects the expression of AQPs and urine output. Rats with ARF showed significant renal insufficiency, and urinary concentration was markedly impaired. In rats with mild ischemic injury (30 min), urine output increased significantly to a maximum at 48 h, and then nearly normalized within 5 days. Consistent with this, semiquantitative immunoblotting revealed that kidney AQP1 and AQP2 abundance was significantly decreased after 24 h to 30 ± 5% and 40 ± 11% ( n = 8) of controls ( n = 9), respectively ( P < 0.05). Five days after ischemia, AQP2 abundance was not significantly decreased and urine output was normalized. In contrast, severe ischemic injury (60 min) resulted in a marked reduction in urine output at 24 h, despite a significant decrease in urine osmolality and solute-free water reabsorption, TcH2O. AQP1 and AQP2 abundance was markedly decreased to 51 ± 5% and 31 ± 9% ( n = 10) of controls ( n = 8) at 24 h ( P < 0.05). After 5 days, the rats developed gradually severe polyuria and had very low AQP2 and AQP1 levels [11 ± 4% and 6 ± 2% ( n = 5) of controls ( n = 8), respectively; P < 0.05]. A similar reduction was observed for AQP3. The reduction in AQP expression in the proximal tubule and inner medullary collecting duct was confirmed by immunocytochemistry. Next, we found that intravenous α-MSH treatment of rats with ARF significantly reduced the ischemia-induced downregulation of renal AQPs and reduced the polyuria. In conclusion, the I/R injury is associated with markedly reduced expression of the collecting duct and proximal tubule AQPs, in association with an impairment of urinary concentration. Moreover, α-MSH treatment significantly prevented the reduction in expression of AQPs and renal functional defects. Thus decreased AQP expression is likely to contribute to the impairment in urinary concentration in the postischemic period.

Cyclooxygenase inhibitors, such as indomethacin and diclofenac, have well-described effects to enhance renal water reabsorption and urinary concentrating ability. Concentrating ability is regulated in part at the level of the thick ascending limb of Henle’s loop, where active NaCl absorption drives the countercurrent multiplication mechanism. We used semiquantitative immunoblotting to test the effects of indomethacin and diclofenac, given over a 48-h period, on the expression levels of the ion transporters responsible for active NaCl transport in the thick ascending limb. Both agents strongly increased the expression level of the apical Na-K-2Cl cotransporter in both outer medulla and cortex. Neither agent significantly altered outer medullary expression levels of other thick ascending limb proteins, namely, the type 3 Na/H exchanger (NHE-3), Tamm-Horsfall protein, or α1- or β1-subunits of the Na-K-ATPase. Administration of the EP3-selective PGE2analog, misoprostol, to indomethacin-treated rats reversed the stimulatory effect of indomethacin on Na-K-2Cl cotransporter expression. We conclude that cyclooxygenase inhibitors enhance urinary concentrating ability in part through effects to increase Na-K-2Cl cotransporter expression in the thick ascending limb of Henle’s loop. This action is most likely due to elimination of an EP3-receptor-mediated tonic inhibitory effect of PGE2on cAMP production.

Body fluid tonicity is controlled largely through the regulation of renal water excretion mediated by the peptide hormone vasopressin ([1][1]). Renal water conservation occurs as a result of the combined functions of the loop of Henle and the collecting duct, both of which are regulated by

Concentrating defect in experimental nephrotic syndrome: Altered expression of aquaporins and thick ascending limb Na + transporters. Background Several pathophysiological states associated with deranged water balance are associated with altered expression and/or intracellular distribution of aquaporin water channels. The possible role of dysregulation of thick ascending limb NaCl transporters, which are responsible for countercurrent multiplication in the kidney, has not been evaluated. Methods Semiquantitative immunoblotting and immunocytochemistry were carried out in the kidneys of rat with adriamycin-induced nephrotic syndrome and in vehicle-injected control rats. Results Preliminary studies confirmed the presence of a severe concentrating defect. Semiquantitative immunoblotting of outer medullary homogenates demonstrated a marked decrease in the abundance of three thick ascending limb Na + transporters in nephrotic rats, namely the bumetanide-sensitive Na-K-2Cl cotransporter (BSC-1), the type 3 Na/H exchanger (NHE-3), and the α 1 -subunit of the Na-K-ATPase. These results are predictive of a decrease in the NaCl transport capacity of the medullary thick ascending limb and therefore a decrease in countercurrent multiplication. Immunocytochemistry of outer medullary thin sections demonstrated broad (but highly variable) suppression of BSC-1 expression in the outer medullas of adriamycin-nephrotic rats. There was also a large decrease in outer medullary expression of two collecting duct water channels (aquaporin-2 and -3) and the major water channel of the thin descending limb of Henle's loop (aquaporin-1). Conclusion The concentrating defect in adriamycin-induced nephrotic syndrome in rats is a consequence of multiple defects in water and solute transporter expression, which would alter both the generation of medullary interstitial hypertonicity and osmotic equilibration in the collecting duct. Whether a similar widespread defect in transporter expression is present in idiopathic nephrotic syndrome in humans is, at this point, untested.

The molecular variants M235T and T174M of the angiotensinogen gene have been linked to essential hypertension in some populations, but there are discrepancies about this association in other studies. We studied 75 patients with essential hypertension (BP > 160/100 mm Hg) from our outpatient clinic, aged 55+/-1 years, 30 men, systolic BP 182+/-2.5, diastolic BP 109+/-1 mm Hg (mean +/- SEM), and a family history of the disease. Target organ damage was evaluated by measuring urinary albumin excretion rate, left ventricular hypertrophy, and fundoscopy. As a control group, 75 healthy subjects with BP < 130/85 mm Hg and with no family history of cardiovascular disease were selected. M235T and T174M angiotensinogen genotypes were determined by PCR and subsequent digestion of the products with SfaNI and NcoI, respectively. The frequency (q) of genotypes of the variant M235T in the patients with essential hypertension was MM 0.31, MT 0.41, and TT 0.28, not significantly different (P = .93) from that of the controls (MM 0.28, MT 0.44, and TT 0.28). For the variant T174M, the genotype frequencies in hypertensives were TT 0.83, TM 0.15, and MM 0.02, which was not significantly different (P = .89) from that of the controls (TT 0.86, TM 0.12, and MM 0.02). Similarly, there was no evidence for association between angiotensinogen genotypes and hypertension in subjects aged < or = 40 years old (n = 24) or with severe (stage III) hypertension (n = 31). Within the group of patients with essential hypertension, there were no differences in genotype distribution between patients with and without retinopathy (n = 31), left ventricular hypertrophy (n = 37), or microalbuminuria (n = 14). This study shows that M235T and T174M variants are not associated either with essential hypertension or with target organ damage in a Spanish sample.

BACKGROUND Hepatitis viruses have become one of the main infectious problems in patients on long-term haemodialysis. A new RNA virus, designated hepatitis G virus (HGV) has been recently identified. The pathogenic relevance of this virus is currently under investigation. The aim of this study was to analyse the prevalence and clinical implications of hepatitis G virus infection in patients on haemodialysis. METHODS The presence of HGV-RNA was investigated in 96 patients on maintenance haemodialysis. Hepatitis viral markers (HBsAg, anti-HCV, HGV-RNA) and liver tests were assessed in all these patients, as well as the risk factors for hepatitis viruses acquisition. As a control group, 200 blood donors were tested for the presence of HGV-RNA. RESULTS HGV-RNA was detected in 25 of 96 patients on haemodialysis (26%) and in six of 200 blood donors (3%) (P < 0.001). Thirteen of 25 HGV infected patients (52%) were coinfected with other hepatitis viruses (HBV and/or HCV). Evidences of chronic liver disease were more frequent in patients infected by HBV and/or HCV (61%) than in patients infected by HGV alone (17%) (P = 0.01). Although 80% of HGV infected patients had received blood products, the transfusion rate was not different from non HGV-infected patients. Time on haemodialysis was significantly shorter in patients infected with HGV alone (3.1 +/- 3.5 years) compared to patients infected with HBV and/or HCV (7.6 +/- 5.8 years) (P = 0.04). CONCLUSIONS Patients on maintenance haemodialysis are at increased risk for HGV infection. HGV infection itself does not seem to be a frequent cause of chronic liver disease in these patients. Since the prevalence of HGV infection in blood donors is high, blood transfusion could be one of the main factors implicated in HGV transmission in patients on haemodialysis.

The kidney plays a central role in the regulation of the salt and water balance, which depends upon an array of solute and water transporters in the renal tubules and upon vascular elements in the various regions of the kidney. Many recent studies have improved our understanding of this process. In this review, we summarize the current data on the molecules involved in sodium and water transport in the renal tubules, focusing in particular on aquaporins and renal sodium transporters and channels.

Urinary exosomes have been proposed as starting material for discovery of protein biomarkers of kidney disease. Current protocols for their isolation use a two-step differential centrifugation process. Due to their low density, exosomes are expected to remain in the low-speed (17,000 × g ) supernatant and to sediment only when the sample is spun at high speed (200,000 × g ). Analysis using western blot and electron microscopy found that urinary exosomes are also present in the low-speed pellet entrapped by polymeric Tamm-Horsfall protein, thus diminishing the procedure's reproducibility. Here we show that addition of dithiothreitol to the low-speed pellet disrupted the polymeric network, presumably by reduction of disulfide bonds linking the monomers. This modification shifted the exosomal proteins from the low- to the high-speed pellet. Also, by shifting the Tamm-Horsfall protein to the high-speed pellet, the use of dithiothreitol makes it feasible to use Tamm-Horsfall protein to normalize excretion rates of exosomal proteins in spot urines. We tested this by western blot, and found that there was a high degree of correlation between exosomal proteins and Tamm-Horsfall protein in the high-speed pellet. Since the yield of exosomes by differential centrifugation can be increased by chemical reduction, Tamm-Horsfall protein may be a suitable normalizing variable for urinary exosome studies when quantitative urine collections are not practical.

Background: Altered renal sodium handling has a major pathogenic role in salt-sensitive hypertension. Renal sodium transporters are present in urinary exosomes. We hypothesized that sodium transporters would be excreted into the urine in different amounts in response to sodium intake in salt-sensitive versus salt-resistant patients. Methods: Urinary exosomes were isolated by ultracentrifugation, and their content of Na-K-2Cl cotransporter (NKCC2) and Na-Cl cotransporter (NCC) was analyzed by immunoblotting. Animal studies: NKCC2 and NCC excretion was measured in 2 rat models to test whether changes in sodium transporter excretion are indicative of regulated changes in the kidney tissue. Human studies: in hypertensive patients (n = 41), we investigated: (1) a possible correlation between sodium reabsorption and urinary exosomal excretion of sodium transporters, and (2) the profile of sodium transporter excretion related to blood pressure (BP) changes with salt intake. A 24-hour ambulatory BP monitoring and a 24-hour urine collection were performed after 1 week on a low- and 1 week on a high-salt diet. Results: Animal studies: urinary NKCC2 and NCC excretion rates correlated well with their abundance in the kidney. Human studies:6 patients (15%) were classified as salt sensitive. The NKCC2 and NCC abundance did not decrease after the high-salt period, when the urinary sodium reabsorption decreased from 99.7 to 99.0%. In addition, the changes in BP with salt intake were not associated with a specific profile of exosomal excretion. Conclusions: Our results do not support the idea that excretion levels of NKCC2 and NCC via urinary exosomes are markers of tubular sodium reabsorption in hypertensive patients.

Background. Mutations in the TRPC6 gene have been reported in six families with adult-onset (17-57 years) autosomal dominant focal segmental glomerulosclerosis (FSGS). Electrophysiology studies confirmed augmented calcium influx only in three of these six TRPC6 mutations. To date, the role of TRPC6 in childhood and adulthood non-familial forms is unknown. Methods. TRPC6 mutation analysis was performed by direct sequencing in 130 Spanish patients from 115 unrelated families with FSGS. An in silico scoring matrix was developed to evaluate the pathogenicity of amino acid substitutions, by using the bio-physical and bio-chemical differences between wild-type and mutant amino acid, the evolutionary conservation of the amino acid residue in orthologues, homologues and defined domains, with the addition of contextual information. Results. Three new missense substitutions were identified in two clinically non-familial cases and in one familial case. The analysis by means of this scoring system allowed us to classify these variants as likely pathogenic mutations. One of them was detected in a female patient with unusual clinical features: mesangial proliferative FSGS in childhood (7 years) and partial response to immunosupressive therapy (CsA + MMF). Asymptomatic carriers of this likely mutation were found within her family. Conclusions. We describe for the first time TRPC6 mutations in children and adults with non-familial FSGS. It seems that TRPC6 is a gene with a very variable penetrance that may contribute to glomerular diseases in a multi-hit setting.

Background and objectives: Autosomal dominant polycystic kidney disease is a systemic disorder with a wide range of extrarenal involvement. The scope of this study was to analyze the prevalence of seminal cysts and to correlate these findings with the sperm parameters in patients with autosomal dominant polycystic kidney disease. Design, setting, participants, & measurements: A prospective study enrolled 30 adult men with autosomal dominant polycystic kidney disease. Of these 30 patients, 22 agreed to provide a semen sample for analysis, and 28 of 30 agreed to undergo an ultrasound rectal examination. Data obtained from the semen tests and from the ultrasound study were compared. Results: Cysts in the seminal tract were present in 10 (43.47%) of 28 individuals. Twenty of 22 patients showed abnormal semen parameters, with asthenozoospermia as the most common finding. No correlation between ultrasound findings and sperm abnormalities was observed. Conclusions: The presence of cysts in the seminal tract is remarkably high (43.47%); however, this finding does not correlate with sperm abnormalities, which are also a frequent finding, especially asthenozoospermia. This semen abnormality is probably related to the abnormal function of polycystins. More attention should be paid to reproductive aspects in the initial evaluation of patients with autosomal dominant polycystic kidney disease before their ability to conceive is further impaired by uremia.

Chronic kidney disease (CKD) is associated with increased mortality. Non-traditional risk factors, such as mineral metabolism disturbances, seem to contribute to the unexpected high mortality rate.

Renal sodium and water reabsorption is mediated by renal sodium transporters and water channels or aquaporins which are localized in the apical and basolateral membranes of tubular epithelial cells. The main apical sodium transporters and water channels located along the nephron are: sodium-proton exchanger subtype 3 (NHE-3) which reabsorbs most of the sodium coming from the glomerular filtrate, sodium-phosphate type II cotransporter (NaPiII) and aquaporin-1, all of which are located in the proximal tubule; sodium-potassium-2 chloride cotransporter (NKCC2) which plays a key role in sodium reabsorption in the thick ascending limb; the sodium-chloride cotransporter (NCC) in the distal tubule; and the epithelial sodium channel (ENaC) and aquaporin-2 located in the collecting tubule. There are some experimental studies in which the role of these proteins has been associated with the pathophysiology of several sodium and water balance disorders. In humans, urine is the perfect source to obtain biomarkers useful for the diagnosis of kidney diseases and the assessment of disease progression without the use of invasive procedures. Thus, some of the renal sodium transporters or the aquaporins located in the apical membrane which are excreted in the tubular lumen and detected in urine could become biomarkers of some sodium and water balance disorders. Nowadays there are many studies investigating the role of these proteins in humans in clinical settings.

Background. Hypertension induced by cyclosporine is associated with renal sodium and water retention. Using immunoblotting of kidney homogenates, we investigated the regulation of sodium and water transport proteins in a rat model of cyclosporineinduced hypertension. Methods. Rats were treated with cyclosporine (25 mg/ kg/day intraperitoneally) during 7 days. Control rats received vehicle. Results. Cyclosporine-treated rats had an increase in blood pressure with a decrease in renal sodium excretion compared with control rats. There were no differences either in sodium intake or in plasma creatinine levels between the two groups of rats. These data suggest that the decrease in sodium excretion in the cyclosporine-treated rats was due to an increase in renal sodium absorption. The densitometric analysis of the renal immunoblot showed an increase in the Na-K-2Cl cotransporter of the loop of Henle (NKCC2) in cyclosporine-treated rats (178% � 36) compared with control rats (100% � 18; P < 0.05 � ). This protein rise was associated with an increase in the NKCC2 mRNA pointing to a transcriptional regulation of this sodium transporter. There were no statistically significant changes in the sodium proton exchange (NHE-3) of the proximal tubule although in this renal segment, aquaporin-1 was increased in cyclosporine-treated rats compared with control rats (control 100% � 6 vs cyclosporine 119% � 6; P < 0.05 � ). Conclusions. Our results pointed to the thick ascending limb of the loop of Henle as an important site of sodium retention in cyclosporine-induced hypertension. This data may have potential clinical implications for the treatment of hypertension induced by cyclosporine.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is a systemic disorder with a wide spectrum of renal involvement. Differences in the age at onset of end-stage renal disease (ESRD) are partially explained by the genetic heterogeneity of the disease but intrafamilial variability remains to be explained. Modifier genes may play a role in disease severity. METHODS: A total of 355 PKD1 patients from 131 families belonging to three different European centres were analysed. According to the age at onset of ESRD patients were classified into two groups: early and late onset. Two different cut-offs were used. Based on literature, early onset was firstly considered when ESRD was reached before 40 years of age and late onset after 60 years of age. Secondly, according to the bimodal distribution of age at onset of ESRD in our population we established two groups with similar variability and the cut-offs were assigned before 48 years of age and after 56 years of age. These groups of patients were then analysed by two different complementary perspectives: (i) using ESRD onset as a quantitative trait when performing survival analysis and Cox regression analysis, and (ii) considering it a qualitative trait. The candidate genes (and polymorphisms) studied were the following: NOS3 (T-786C and E298D), BDKRB1 (-699 G > C), BDKRB2 (R14C), TGFB1 (-509 C > T, R25P and L10P), ACE (I/D), EGFR (IVS1CA) and PKD2 (-9780 G > A, -718 A > G and 83 C > G). RESULTS: The results disclosed that the ACE polymorphism had a slight influence on the age of onset of ESRD in ADPKD patients and the NOS3 and BDKBR1 polymorphisms showed a very slight involvement in renal outcome. CONCLUSIONS: Our results discard the most prominent functional genes suggested to date, to have a major effect on ADPKD progression in this cohort. Genes strongly implicated in disease severity are yet to be identified. The description of such genes would allow us to establish a prognosis for ADPKD and eventually to develop therapeutic interventions.

Several experimental models of cirrhosis have shown dysregulation of renal aquaporins in different phases of liver disease. We investigated the urinary excretion of both aquaporin-1 and aquaporin-2 in patients with cirrhosis at different stages of the disease. Twenty-four-hour urine was collected from 11 healthy volunteers, 13 patients with compensated cirrhosis (without ascites), and 20 patients with decompensated cirrhosis (11 with ascites without renal failure and 9 with hepatorenal syndrome). Aquaporin-1 and aquaporin-2 excretion was analyzed by immunoblotting. Urinary aquaporin-2 excretion was reduced in patients with cirrhosis compared to healthy subjects. A progressive decrease in urinary aquaporin-2 excretion was observed as the severity of cirrhosis increased, from compensated cirrhosis to cirrhosis with ascites and hepatorenal syndrome. Patients with hyponatremia had lower urinary aquaporin-2 excretion than patients without hyponatremia. Vasopressin plasma level did not correlate with aquaporin-2 excretion. There were no differences between healthy subjects and patients with cirrhosis with or without ascites in urinary excretion of aquaporin-1, but urinary aquaporin-1 excretion of those with hepatorenal syndrome was extremely low. In conclusion, patients with cirrhosis appear to exhibit a decreased abundance of renal aquaporin-2 and therefore lower water permeability in the collecting tubules. This may represent an adaptive renal response to sodium retention, with expansion of extracellular fluid volume and dilutional hyponatremia observed in those who have cirrhosis with ascites. Finally, aquaporin-1 does not appear to play a role in the progressive dysregulation of extracellular fluid volume in cirrhosis.

Background Alport syndrome (AS) is a genetically heterogeneous hereditary renal disease. X-Linked AS (XLAS) is responsible for 80% to 85% of familial cases and is caused by mutations in the COL4A5 collagen gene. To date, indirect molecular diagnosis for XLAS is not well defined, and mutation screening of the COL4A5 gene is time consuming and complicated because of its large size and high allelic heterogeneity. Our aim is to facilitate XLAS genetic testing. Methods For linkage analysis, we tested the applicability of 4 microsatellite markers defining a 1.2-megabase region flanking the COL4A5 gene. For mutation screening of the COL4A5 gene, we describe a new strategy based on direct sequencing of hair root COL4A5 messenger RNA (mRNA). Results Three microsatellite markers proved accurate ( DXS1120 , DXS6802 , and DXS1210 ) and 1 was discarded ( DXS6797 ) because it was difficult to interpret. The mutation screening method provides results in 4 days, and when applied to 29 patients suspected of having XLAS, it identified mutations in 76% (22 of 29 patients). This study correlates COL4A5 mutations with effects at the mRNA level and suggests that mutations affecting mRNA splicing of the COL4A5 gene (41%; 9 of 22 patients) are more common than previously described. Many splicing mutations did not alter the canonical 5′ and 3′ splice sites. Conclusions A more reliable linkage analysis and a simple, fast, and efficient mutation screening are now available for the genetic testing of patients with XLAS.

Sodium retention in cirrhotic rats is associated with increased renal abundance of sodium transporter proteins. Background Liver cirrhosis with ascites is associated with a decrease in renal sodium excretion and therefore sodium retention. Methods In this paper, we utilize transporter-specific antibodies to address the hypothesis that dysregulation of one or more sodium transporters or channels is associated with sodium chloride (NaCl) retention in a rat model of cirrhosis induced by repeated exposure to carbon tetrachloride. Age-matched controls and cirrhotic rats were pair fed to ensure identical NaCl and water intake for 4 days prior to euthanasia for quantitative immunoblotting studies. Results and Conclusion The rats manifested marked extracellular fluid volume expansion with massive ascites. Plasma aldosterone levels were markedly elevated. Analysis of immunoblots revealed marked increases in the abundances of both of the major aldosterone-sensitive apical transport proteins of the renal tubule, namely the thiazide-sensitive NaCl cotransporter NCC and the epithelial sodium channel alpha subunit (α-ENaC). These results are consistent with an important role for hyperaldosteronism in the pathogenesis of sodium retention and ascites formation in cirrhosis. In addition, we observed a large decrease in cortical NHE3 abundance (proximal tubule) and a large increase in NKCC2 abundance (thick ascending limb), potentially shifting premacula densa sodium absorption from proximal tubule to loop of Henle (which powers urinary concentration and dilution).

Background/Aims Ascites in patients with cirrhosis is associated with worsening of systemic hemodynamics. Thus, the aim of this study was to investigate the biological activity of ascites on endothelial cells. Methods Human umbilical vein endothelial cells (HUVECs) were used to investigate the angiogenic activity of ascites obtained from cirrhotic patients. Results Ascites-induced Akt activation, cell migration and tube formation in HUVECs. The pretreatment of HUVECs with the phosphatidylinositide 3-kinase (PI3-kinase) inhibitor LY294002, resulted in a decrease in chemotaxis and cell tube formation induced by ascites. Moreover, the inhibition of Akt activity in HUVECs by transduction of an inactive phosphorylation Akt mutant (AA-Akt), blocked tube formation. These angiogenic effects of ascites were also operative in vivo showing a PI3-kinase activation dependence in the angiogenesis induced by ascites. In addition, the preincubation of ascites with anti-fibronectin antibody led to a significant decrease in HUVECs migration, cell tube formation and in vivo angiogenesis. Conclusions These results confirm the novel concept that ascites is a bioactive fluid which can modify vascular properties through the activation of the PI3-kinase/Akt pathway in endothelial cells. Furthermore, our results demonstrated that this ascites-induced mechanism is mediated, at least in part, by fibronectin.

Previous studies have established that the vasopres- sin-regulated water channel of the collecting duct, aquaporin-2, is excreted in the urine, providing a means for assessment of regulation and dysregulation of aquaporin-2 in humans. This article addresses the hypothesis that membrane transporters from upstream nephron segments are normally detectable in urine. The experiments employed rabbit polyclonal antibodies against the major Na transporters of the proximal tubule (the type 3 Na-H exchanger (NHE3)), the thick ascending limb of Henle's loop (the bumetanide-sensitive Na-K-2Cl cotrans- porter (NKCC2)), and the distal convoluted tubule (the thia- zide-sensitive Na-Cl cotransporter (NCC)) in immunoblotting experiments. All three of these transporters were readily de- tectable as high molecular weight complexes present in low- density membrane fractions from urine of normal rats. Cross linking studies of NHE3, NKCC2, and NCC revealed that high molecular weight complexes are normally present in renal tissue. The molecular weights of the complexes in urine matched those of the cross-linked complexes in native kidney tissue. The presence in urine of integral membrane proteins representative of each nephron segment raises the possibility that limited or comprehensive proteomic analysis of urine samples may be useful in clinical settings.

In chronic renal failure (CRF), reduction in renal mass leads to an increase in the filtration rates of the remaining nephrons and increased excretion of sodium per nephron. To address the mechanisms involved in the increased sodium excretion, we determined the total kidney levels and the densities per nephron of the major renal NaCl transporters in rats with experimental CRF. Two weeks after 5/6 nephrectomy (reducing the total number of nephrons to ∼24 ± 8%), the rats were azotemic and displayed increased Na excretion. Semiquantitative immunoblotting revealed significant reduction in the total kidney levels of the proximal tubule Na transporters NHE-3 (48% of control), NaPi-II (13%), and Na-K-ATPase (30%). However, the densities per nephron of NHE-3, NaPi-II, and Na-K-ATPase were not significantly altered in remnant kidneys, despite the extensive hypertrophy of remaining nephrons. Immunocytochemistry confirmed the reduction in NHE-3 and Na-K-ATPase labeling densities in the proximal tubule. In contrast, there was no significant reduction in the total kidney levels of the thick ascending limb and distal convoluted tubule NaCl transporters BSC-1 and TSC, respectively. This corresponded to a 3.6 and 2.5-fold increase in densities per nephron, respectively (confirmed by immunocytochemistry). In conclusion, in this rat CRF model: 1) increased fractional sodium excretion is associated with altered expression of proximal tubule Na transporter expression (NHE-3, NaPi-II, and Na-K-ATPase), consistent with glomerulotubular imbalance in the face of increased single-nephron glomerular filtration rate; and 2) compensatory increases in BSC-1 and TSC expression per nephron occur in distal segments.