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The study examined whether indexing glomerular filtration rate (GFR) for body surface area is appropriate for people who are severely overweight. Twenty normotensive adult men who were severely overweight but without microalbuminuria were enrolled into this study. The control group consisted of 20 healthy subjects matched for age, sex, and height. GFR was determined by measuring insulin with the continuous-infusion method. The clearance of endogenous creatinine was also measured after two daily urine collections. Renal plasma flow (RPF) was measured by p-aminohippurate clearance using the continuous-infusion method. Lean body weight was measured by impedentiometry. Adjusting for body surface area (in 1.73 m(2)) caused a significant reduction in GFR (P0.0001) in overweight humans (84.1 +/- 2.32 versus 109.6 +/- 3.07 mL/min/1.73 m(2)). The difference disappeared when GFR/height criteria were adopted. No difference between obese and healthy controls occurred after adjusting for lean body weight. Data for creatinine clearance paralleled those with insulin clearance; a significant reduction (P0.001) occurred after indexing for basal surface area, which disappeared after correction for height, as well as for lean body weight.

Patients with advanced heart failure commonly develop simple or mixed acid-base disturbances. The altered acid-base homeostasis can occur as a consequence of the heart failure itself, the therapeutic interventions, or associated conditions. The present study examined acid-base disorders in patients with heart failure who received successful heart transplantation. The information collected should provide light on the determinants of acid-base disorders in this patient population. Seventy status 2 UNOS (United Network Organ Sharing) patients listed for heart transplantation were enrolled in this study. All patients received loop diuretics, spironolactone, ACE inhibitors, carvedilol and digitalis as needed. Patients were studied again at discharge after transplantation, under cyclosporine, azathioprine, steroids, loop diuretics and ACE inhibitors. After heart transplantation, a significant increase of ejection fraction from 19.7 ± 0.63 to 53.6 ± 0.9% (p < 0.0001) occurred along with a concomitant reduction of central venous pressure (p < 0.0001) from 12.6 ± 0.20 to 6.9 ± 0.21 mm Hg. Before heart transplantation there was high-normal pH (7.43 ± 0.009), slight loss of hydrogen ions (35.4 ± 0.4 nmol/l), slightly reduced pCO2 (37.6 ± 1.1 mm Hg). After heart transplantation a stability of blood pH and hydrogen ion concentrations was found but bicarbonate increased significantly (p < 0.02) from 24.2 ± 0.61 to 26.2 ± 0.51 mmol/l and pCO2 from 37.6 ± 1.1 to 39.3 ± 0.7 mm Hg (p < 0.05). Plasma renin activity averaged 3.80 ± 0.6 pg/ml before heart transplantation and 2.82 ± 0.4 pg/ml after (p < 0.01). Aldosterone concentration averaged 380 ±15 pg/ml before heart transplantation and 280 ± 10 pg/ml after (p < 0.01). These data suggest that in patients before heart transplantation there is a mixed acid-base imbalance that includes respiratory alkalosis and metabolic alkalosis. After transplantation the recovery of the abnormal circulatory status erased the initial respiratory alkalosis but metabolic alkalosis persisted and accounted for a further rise in plasma bicarbonate.

Renal reserve was explored by means of an oral protein load (2 g/kg body weight) under the form of cooked red meat in a group of 9 patients with end-stage heart failure (ESHF), class III of the New York Heart Association receiving loop diuretics and angiotensin-converting enzyme (ACE) inhibitors, and in a group of 18 healthy controls (HC) matched for age, gender, and height under an identical dietary regimen providing 40 cal/kg per day, 1 g/kg body weight of protein per day, Na 120 mmol/day, and K 50 mmol/day. Baseline glomerular filtration rate averaged 109.5±9.89 ml/min×1.73 m2 in HC and 71.9±8.8 ml/min×1.73 m2 in ESHF. Renal plasma flow averaged 540±27 ml/min×1.73 m2 in HC and 235±47 ml/min×1.73 m2 in ESHF. The filtration fraction was significantly higher in ESHF (p2 in HC and 27.2±7.12 ml/min×1.73 m2 (not significant). Renal reserve averaged 123.9±2.9% in HC and 137.3±6.68% in ESHF (not significant). The filtration capacity was significantly higher in HC (p

This study adds another category of patients to those amenable to body impedance analysis (BIA). BIA measurements were obtained for the first time in 23 male patients with end-stage heart failure who were waiting for heart transplantation, and the data were compared with those obtained in 69 healthy controls matched for age, sex, height and weight. The data indicate that in end-stage heart failure there is an increased reactance (p

The study was devised to explore the effects of an acute oral protein load on renal hemodynamic response in patients with IgA nephropathy (IgAN). The study was performed in 10 proteinuric IgAN patients (800 ± 300 mg/day) and in 20 healthy controls (matched by sex, age, BMI, BSA, plasma creatinine, plasma urea, urinary urea and protein intake). Blood pressure and creatinine clearance were nearly identical in the two groups. GFR. and RPF, measured as the clearance of inulin and of p-aminohippurate (PAH) were studied before and after a meat meal which provided 2 g of protein/kg BW. Following the protein load, renal reserve, percent renal reserve and postmeal cumulative changes of GFR were not significantly different in IgAN and controls. Filtration fraction (FF) at baseline was significantly higher (p < 0.01) in IgAN than in controls (25.5 ± 1.41 vs. 19 ± 2%). Postmeal hyperemia and hyperfiltration did not affect FF in either group. Filtration capacity in IgAN was lower (p < 0.02) than in controls (117 ± 5.6 vs. 137.9 ± 7.0ml/min × 1.73 m2), whereas the percent of filtration capacity utilized at rest was identical in controls and in IgAN. Creatinine clearance overestimated GFR in IgAN. The data indicate that renal hemodynamic response to proteins in IgAN is normal. © 1997 S. Karger AG, Basel.

Glomerular filtration rate (GFR) was measured in 19 patients with Child A liver cirrhosis by comparing the endogenous creatinine clearance with inulin clearance. Inulin clearance averaged 90 +/- 4.4 ml/min x 1.73 m2, while creatinine clearance averaged 122 +/- 7 ml/min x 1.73 m2 (p < 0.001). The overestimation of GFR by creatinine was present in 18 of 19 patients and was inversely correlated with inulin clearance (r = -0.452, p < 0.04). The data point to the unsuitability of creatinine as a marker of filtration in early posthepatitic cirrhosis (Child A).

In this study Bioelectrical Impedance Analysis was performed in 5 patients with end stage heart failure in whom a left ventricular assist device (Novacor) was successfully implanted. Whole body measurements of bioelectrical indices resistance and reactance were taken before surgery and 3, 7, 12, and 15 days after it. After surgery there was a significant decrease in reactance, indicating a shift of body fluids from intra- to extra-cellular space.

The study was devised to establish the role of prostaglandin E(2), prostaglandin(In), and thromboxane A(2) in the genesis of glomerular hyperfiltration response to a meat meal in healthy humans. To this end, a group of 8 healthy women was studied 4 times: in the control state (study 1), after a meat meal (study 2), following a meat meal associated with intravenous aspirin (study 3) and finally after a meat meal associated with intravenous aspirin following 2-day pretreatment with oral aspirin (study 4). Urinary excretion of prostaglandins and thromboxane increased during the glomerular hyperfiltration response to a meat meal and was suppressed by aspirin administration which did not suppress the renal hemodynamic response to the meat meal. The data do not support a causal role for prostaglandins and thromboxane A(2) in the hemodynamic response to acute protein loading.

Background/Aims: Little information is available about the tubular functions and the renal adjustments that take place in obese subjects after a protein meal. How the excess fat may affect renal response to dietary proteins is currently only partially understood. This paper aims to address (i) whether severe obesity, in the absence of other comorbidities, is responsible of kidney dysfunction at either the glomerular or the tubular level and (ii) whether it compromises renal adaptations to a large protein meal. Methods: Twenty-eight obese subjects without albuminuria, along with 20 control subjects, age and gender matched, have been studied. The glomerular filtration rate (GFR; inulin clearance), renal plasma flow (p-aminohippurate clearance), the proximal tubular function (lithium clearance), the fractional excretion of sodium (FPRNa) have been measured at the basal level (steady state) and after a protein meal (perturbation). Results: Under steady state conditions, filtration fraction, proximal tubular sodium handling and the FPRNa were not significantly different in non proteinuric obese subjects compared with controls. However, a protein meal led to a delayed glomerular hyperfiltration in obese patients compared with controls. Conclusion: This study shows that obese patients, in the absence of significant comorbidities, have a normal proximal tubule Na+ absorption at basal; conversely, these subjects showed a different response to a protein meal compared with normal subjects in terms of changes of GFR. Overall, these results suggest that the modified hemodynamic response to a protein meal might be the earliest hallmark of future kidney dysfunction in obese subjects.

Introduction. Extracellular sodium (Na+) concentration is maintained within a tight physiological range due to hormonal control, that mainly modulates thirst, Na+ and water renal excretion. Extra-renal regulation of Na+ and water homeostasis is only partially understood. Recently it has been debated whether the osmotically inactive Na+ storage is fixed or variable. Methods. In the present study, fourteen End-Stage Renal Disease (ESRD) patients treated by chronic hemodialysis underwent by accident to a sharp increase in plasmatic calcium (Ca+2) levels due to the failure of the water control system, leading to the so-called hard water syndrome. The levels of plasmatic Ca+2 after 1 hr of hemodialysis were correlated with urea, Na+, potassium (K+) and creatinine levels. Eleven ESRD patients treated with hemodialysis under similar conditions were used as controls. Results. The hard water syndrome resulted in hypercalcemia, while mean plasma levels of Na+, K+ and urea were not different compared to controls. Plasma creatinine levels were slightly but significantly higher that control. A correlation analysis on the measured variables has showed a positive correlation between plasma Ca+2 and Na+ levels (Pearson=0.428, p=0.032), and the absence of any correlation with K+, creatinine and urea concentration. Conclusions. Our study suggests that acute changes in plasmatic Ca+2 levels may affect Na+ concentration in the absence of renal function; it is possible that hypercalcemia may trigger Na+ release from the osmotically inactive storage. These data further support previous observations on the interplay of sodium and calcium at extrarenal sites.

Tuberous sclerosis complex (TCS) is a genetic disorder with a variable clinical presentation. It is commonly characterized by seizures, mental retardation and cutaneous angiofibromas. Renal manifestations frequently include angiomyolipomas and cysts which lead to chronic kidney disease. We report a case of valproic acid-induced acute pancreatitis in a dialysis patient affected by TCS. The case demonstrates the importance of assessing antiepileptic drug treatment in dialysis patients. © 2012 Società Italiana di Nefrologia.

This article reviews bone adaptation to microgravity, during manned space missions, in humans undergoing Head Down Tilt (HDT) and in Hind-Limb-Suspended Rats. Under microgravity conditions, bone loss occurs in association with hypercalciuria, which in turn modulates Aquaporin 2 (AQP2) excretion in urine, thus avoiding stone forming in space. This report discloses the need to prevent bone loss in order to prepare for long stays at lunar bases or voyages to Mars. (C) 2005 by the National Kidney Foundation, Inc.

Background. Cyclosporine A (CsA) is one of the most frequently used anticalcineurinic drugs for preventing graft rejection and autoimmune disease. Its use is hampered by nephrotoxic effects, namely an impairment of the glomerular filtration rate (GFR) and hypertension. Evidence suggests that reactive oxygen species (ROS) play a causal role in the nephrotoxicity. The present study aims to investigate in vivo the effects of a new recombinant mitochondrial manganese-containing superoxide dismutase (rMnSOD), a strong antioxidant, on the CsA-induced nephotoxicity. Methods. Rats were treated with CsA (25 mg/kg/day) alone or in combination with rMnSOD (10 μg/kg/day) for 7 days. At the end of the treatment, GFR was estimated by inulin clearance (mL/min/100 g b.w.) and the mean arterial pressure (MAP) was recorded through a catheter inserted in the carotid artery. Superoxide concentration within the cells of the abdominal aorta was quantified from the oxidation of dihydroethidium (DHE). In kidney tissues, ROS levels were measured by the 2′7′ dichloroflurescin diacetate assay. Renal morphology was examined at the histochemistry level. Results. CsA-treated rats showed a severe decrease in GFR (0.34 ± 0.17 versus 0.94 ± 0.10 in control, P < 0.001) which was prevented by rMnSOD co-administration (0.77 ± 0.10). CsAinjected animals presented with higher blood pressure which was unaffected by rMnSOD. ROS levels both in the aorta and in renal tissue were significantly increased by CsA treatment, and normalized by the co-administration with rMnSOD. This effect was, partly, paralleled by the recovery from CsA-induced morphological lesions. Conclusions. Administration of rMnSOD prevents CsA-mediated impairment of the GFR along with morphological alteration. This effect could be related to the inhibition of ROS. © The Author 2012.

Renal dysfunction is a constant feature of congestive heart failure and is a stronger predictor of mortality than left ventricular ejection fraction or New York Heart Association classification. In heart failure, a reduction of glomerular filtration rate and renal plasma flow occurs, although the filtration fraction increases. There are many reason for this pattern. A reduction in effective circulating volume stimulates sympathetic activity and the renin-angiotensin-aldosterone system, and it is associated with increased concentrations of atrial natriuretic peptide, brain natriuretic peptide, and tumor necrosis factor α. Because in chronic kidney disease heart dysfunction commonly is present, an efficient cardiologist-nephrologist interaction should be promoted. © 2005 Elsevier Inc. All rights reserved.

Background. Previous studies have shown conflicting data on accuracy of equations for kidney function prediction. The present work analysed the relationship of gender, age and body mass index (BMI) to error of predictions by the Cockcroft–Gault equation (CGeq), the simplified equation of the Modification of Renal Diseases Study (MDRDeq) and the Mayo Clinic equation (Mayoeq). Methods. Inulin clearance (glomerular filtration rate; GFR) and other variables were measured in 380 subjects of both sexes, aged 18–88 years, with and without kidney disease. GFR was defined as low when

Clinical studies indicate that indices of glomerular filtration rate (GFR) as serum creatinine or creatinine clearance can predict the risk of death in congestive heart failure (CHF) and in heart transplantation. The study reports data on creatinine clearance before and after heart transplantation in 160 patients followed-up for 5 years at our Unit. Pre-transplant creatinine clearance averaged 83.5*32 mL/min * 1.73 m2 and was not significantly associated with 5-year mortality. Creatinine clearance significantly decreased after heart transplantation with a linear trend up to 3 years for patients with complete follow-up. Data suggest that the relation between kidney function and mortality after heart transplantation is affected by several confounders with inclusion of cause of heart disease, co-morbidity, anemia, and post-transplant decrease in kidney function. Clinical studies indicate that indices of glomerular filtration rate (GFR) as serum creatinine or creatinine clearance can predict the risk of death in congestive heart failure (CHF) and in heart transplantation. The study reports data on creatinine clearance before and after heart transplantation in 160 patients followed-up for 5 years at our Unit. Pre-transplant creatinine clearance averaged 83.5±32 mL/min × 1.73 m 2 and was not significantly associated with 5-year mortality. Creatinine clearance significantly decreased after heart transplantation with a linear trend up to 3 years for patients with complete follow-up. Data suggest that the relation between kidney function and mortality after heart transplantation is affected by several confounders with inclusion of cause of heart disease, co-morbidity, anemia, and post-transplant decrease in kidney function. © 2005 Elsevier Inc. All rights reserved.

Patients with end-stage renal disease are prone to hemorrhagic complications and simultaneously are at risk for a variety of thrombotic complications such as thrombosis of dialysis blood access, the subclavian vein, coronary arteries, cerebral vessel, and retinal veins, as well as priapism. The study was devised for the following purposes: (1) to identify the markers of thrombophilia in hemodialyzed patients, (2) to establish a role for antiphospholipid antibodies in thrombosis of the vascular access, (3) to characterize phospholipid antibodies in hemodialysis patients, and (4) to study the effects of dialysis on coagulation cascade. A group of 20 hemodialysis patients with no thrombotic complications (NTC) and 20 hemodialysis patients with thrombotic complications (TC) were studied along with 400 volunteer blood donors. Patients with systemic lupus erythematosus and those with nephrotic syndrome were excluded. All patients underwent a screening prothrombin time, activated partial thromboplastin time, fibrinogen (Fg), coagulation factors of the intrinsic and extrinsic pathways, antithrombin III (AT-III), protein C (PC), protein S (PS), resistance to activated protein C, prothrombin activation fragment 1+2 (F1+2), plasminogen, tissue type plasminogen activator (t-PA), plasminogen tissue activator inhibitor type-1 (PAI-1), anticardiolipin antibodies type M and G (ACA-IgM and ACA-IgG), lupus anticoagulant antibodies, and antiprothrombin antibodies type M and G (aPT-IgM and aPT-IgG). The study showed that PAI-1, F 1+2, factor VIII, ACA-IgM, and aPT-IgM levels were increased significantly over controls both in TC and NTC, however, they could distinguish patients with thrombotic complications from those without, being increased maximally in the former group. The novelty of the study is represented by the significant aPT increase that was observed in non–systemic lupus erythematosus hemodialysis patients, and particularly in those with thrombotic events. In addition, there was a reduction of factor XII during the treatment. It is possible to assume in the TC group and, to a lesser extent, also in the NTC group that endothelial cells liberate PAI-1 in the vascular lumen, which causes hypofibrinolysis. In addition, an excess of factor VIII is activated by endothelial dysfunction with subsequent activation of the coagulation cascade as shown by increased F1+2 and fibrinogen. ACA-IgM, in turn, is capable of interfering with the system of protein C, a potent anticoagulant factor that inactivates cofactors Va and VIIIa. They also induce the expression of procoagulant factors on the surface of the endothelial cells. In conclusion, the hypercoagulable state caused by alterations of coagulation and fibrinolytic factors is a cause of vascular access dysfunction and thrombosis of other vessels.

Level of hydration and renal function in healthy humans. Background High hydration is commonly used in renal studies to improve the completeness of urine collection. The renal effects of hydration are not well defined. Methods Renal function was studied under fasting conditions (baseline) and after a meat meal (2g of protein/kg body weight) in 12 healthy adults on a low and high hydration regimen of 0.5 and 4mL of oral water perkg body weight/30 min, respectively. Results Urine flow, urinary and plasma Na, K, urea, and osmolality were stably different on low and high hydration regimens. At baseline, there were significant or borderline significant correlations of plasma and urine osmolality with glomerular filtration rate (GFR; inulin clearance) only in the low hydration regimen. GFR was higher in the low than the high hydration regimen at all time points. The difference was significant at baseline (19.2%) and at 90 to 180 minutes after the meal (14.4%). After the meal, GFR increased significantly over baseline values only in the high hydration regimen (30.0% at peak time). Urinary excretion of Na, urea, and osmoles was lower in the low than the high hydration regimen at all time points: The difference was significant for Na (at baseline) and osmoles (all time points). Urinary K excretion was not different in the two regimens. After the meal, there were significant increases in urinary excretion of Na (in the low hydration regimen) and urea (90 to 180min after the meal). Conclusions In fasting adults, high hydration lowered GFR and increased natriuresis. After a meat meal, GFR increased only in the high hydration regimen and natriuresis only in the low hydration regimen. Hydration affects GFR and natriuresis under fasting conditions and after a meat meal.

Cardiovascular disease is the leading cause of morbidity and mortality in end-stage renal disease. Causes include those usually found in the general population, those related to the uremic status, and those related to dialytic treatment. Hypertension, hypotension, anemia, hypoalbuminemia, malnutrition, dyslipidemia, reactive C protein, calcium-phosphate product, dialysis modalities, and hyperhomocysteinemia are discussed extensively. Special emphasis is put on hyperparathyroidism as a traditional toxin. The emergent role of sleep apnea has been confirmed in animal models as well as in humans studied using polysomnography. There are difficulties in diagnosing coronary disease, because angiography is not risk-free, is expensive, and should be reserved for patients having symptoms of heart failure and/or patients having diabetes mellitus, and/or patients entering a transplantation list. This allows patients with coronary disease to undergo coronary artery bypass (preferably) or percutaneous transluminal angioplasty. Patients for whom surgery is not appropriate should be treated using more traditional medical procedures. (C) 2001 by the National Kidney Foundation, Inc.

The work was designed to study the effects of a meat meal on glomerular filtration rate (GFR), renal plasma flow (RPF), and plasma concentrations of glucagon, insulin, growth hormone, renin, aldoster-one, total amino acids, and NH3 in healthy humans (H) as well as in patients with Child A liver cirrhosis (LC). The meat meal produced renal hyperaemia and hyperfiltration without changes in the filtration fraction. Fractional Na excretion in urine increased significantly after the meat meal only in LC. Hyperinsulinae-mia and hyperglucagonaemia were seen at baseline in LC and were not affected by the meat meal, whereas in H glucagon concentration increased significantly over baseline within 30 min from the meat meal and insulin within 60 min. Growth hormone concentration was normal at baseline in LC and increased significantly 120–180 min after the meal, whereas it was not affected in H. Renin and aldosterone were stable in both H and LC. Plasma amino acid concentration began to increase 60 min after the meat meal, when hyperfiltration was present. The data indicate that in human Child A cirrhosis of the liver the renal haemodynamic response to a meat meal is independent of changes in glucagon.

The effect of an acute protein load (2 g kg‐1bodyweight [BW]) was studied in nine type 1 diabetic children. Patients were maintained on two different dietary regimens. In study one, patients were on a high protein diet providing from 2.7 to 1.8 g of protein/kg of BW per day. In study two, patients were reevaluated after three weeks of a diet providing from 1.0 to 1.2 g kg‐1 of BW per day of protein. In study one (High Protein Diet), we failed to observe any rise in GFR and RPF following the protein meal (137 ± 21 basal vs. 110±14 and 472±93 basal vs. 494±93 ml/1.73 m2 of SA min‐1 at 60 min. This is in contrast with results from seven age matched controls consuming a free diet, which showed a significant rise in both GFR and RPF. In study two (low protein diet), basal GFR was significantly reduced. However after the protein load, both GFR (92±11 vs. 126±18 ml/1.73 m2 of SA min‐1) and RPF (467±83 vs. 705±102 ml/1±73 m2 min‐1) rose significantly (P

The organometal cisplatin has potent antitumor properties. However, its use is sometimes complicated by significant nephrotoxicity. This is characterized by tubular necrosis and impairment of the glomerular filtration rate (GFR). On the other hand, it has been demonstrated that atrial natriuretic factor (ANF) increases GFR in normal euvolemic rats. In the present study, we have therefore tested if this new potent natriuretic compound could restore some of the renal parameters affected by cisplatin. To investigate this issue, acute renal failure was induced in 9 rats by intraperitoneal injection of cisplatin 10 mg/kg body weight (b.w.). Renal function was studied 72 h later using the 3H-inulin clearance method and was compared with the renal function of 5 normal euvolemic rats. The cisplatin-treated rats showed high blood urea nitrogen levels, a 74% reduction of whole kidney GFR (0.308 +/- 0.047 vs. 1.17 +/- 0.08 ml/min/100 g b.w.) and a significant increase in the fractional excretion of urine, sodium and potassium. After 2 control clearances, synthetic ANF was administered intravenously as a prime (12 micrograms/kg b.w.) and then as a constant infusion (1 microgram/kg/min) to 6 cisplatin-treated rats. This promptly doubled the GFR (0.603 +/- 0.113 ml/min/100 g b.w.) and induced a significant increase in the excretion rate of urine, sodium and potassium. These results demonstrate that the administration of ANF has a beneficial effect on the experimental model of acute renal failure induced by cisplatin.

The work was designed to assess the suitability of both measured endogenous creatinine clearance (C(CR)) and predicted creatinine clearance (P-C(CR)) to evaluate GFR in chronic renal disease (CRD) by utilizing the renal clearance of inulin (C(IN)) as gold standard. A total of 124 subjects were studied (62 healthy, 62 with CRF). C(CR) significantly overestimated GFR in healthy subjects as well as in CRF, whereas P-C(CR) was identical to GFR. The C(CR)/C(IN) ratio which calculates the fractional creatinine clearance and provides a rough estimation of the contribution of creatinine secretion in explaining the differences between C(CR) and GFR was increased in CRD and especially in CRD of glomerular origin. The ration P-C(CR)/C(IN) was significantly lower than C(CR)/C(IN) in healthy subjects and in patients with CRD of glomerular origin. The data are against the use of C(CR) in assessing GFR in healthy subjects and in patients with CRD.

The renal hemodynamic response to a meat meal (2 g/kg BW) was studied in 11 healthy children and in 10 children with a mean plasma creatinine concentration of 2.6 +/- 0.1 mg/dl due to chronic renal failure (CRF) of various etiologies. In the healthy status, after a meat meal, the glomerular filtration rate (GFR) increased significantly from a baseline value of 119.0 +/- 5.0 to a peak of 159 +/- 5.8 ml/min x 1.73 m2; in CRF baseline GFR averaged 49 +/- 4.0 and at peak 76.6 +/- 7.2 ml/min x 1.73 m2 (p less than 0.005). The peak GFR response was reached earlier in healthy subjects than in CRF (p less than 0.05) and did not correlate with age or with baseline GFR. Renal plasma flow (RPF) in healthy controls increased from 532 +/- 32 at baseline to 646 +/- 42.9 ml/min x 1.73 m2 after the meal (p less than 0.005). Also in CRF after a meat meal there was a significant increase in RPF from 278 +/- 51 to 65 +/- 66 ml/min x 1.73 m2 (p less than 0.005). The filtration fraction was not affected. The percent increase over baseline values of GFR and RPF at the peak was significantly higher in diseased children. Renal reserve averaged 28.1 +/- 5.3 ml/min in diseased children and 39.7 +/- 5.2 ml/min (p less than 0.01). The data indicate that (1) a meat meal is a suitable method to recruit renal reserve in normal children and in children with chronic renal failure, and (2) the renal reserve is normal in chronic renal failure.

Thyroid hormones affect the functions of several organs including the heart and kidney. Using isolated left papillary muscles we have investigated the action of thyroid hormones on the mechanical and electrical properties of the heart. We found that pure hypothyroidism causes a depression in contractile and electrical parameters, but we noticed that superimposed hypoparathyroidism accounts for the marked prolongation in contractile kinetics and action potential duration. At kidney level we have shown that thyroid hormones affect proximal tubular sodium transport and this effect is only partially mediated by the action of thyroid hormones on Na-K-ATPase activity. Using the micropuncture technique, we hypothesized that the early effect of thyroid hormone action is on the potassium permeabilty of proximal tubular cell membrane. This latter effect would explain the increase in isotonic fluid reabsorption through an increase in the driving force for sodium. Finally, hypothyroid patients have a decrease in glomerular filtration rate and renal plasma flow that are completely reversed by thyroxine administration. On the other hand, hyperthyroid subjects exhibit a significant increase in both parameters.

The effect of a meat load on the renal handling of acid-base balance was studied in ten healthy subjects (GFR by inulin clearance = 98.5 +/- 8.14 ml.min-1.1.73 m-2) and in ten patients affected by chronic renal failure (CRF) (GFR = 39.9 +/- 5.3 ml.min-1.1.73 m-2). After the meat load (2 g.kg-1 body weight of cooked unsalted red meat), GFR increased by 26.9% (peak value) over baseline in healthy subjects and by 32% in CRF patients. The acid-base status of the healthy subjects was in the normal range, whereas the CRF patients disclosed a slight metabolic acidosis. After a meat load, there was, in the healthy subjects, an increase in the filtered load of bicarbonate coupled to an enhanced tubular reabsorption and urinary excretion. The time course between bicarbonate load and urinary excretion was coincident. In CRF patients, the increase of bicarbonate tubular load after the meal was associated with an increase in tubular reabsorption but not in urinary excretion of this anion. The relationship between bicarbonate load and reabsorption was linear in both groups up to the highest filtered loads. Baseline titratable acidity (TA) and ammonium (NH4+) excretion (expressed per ml GFR) were increased in CRF patients as compared with control subjects, but no changes were found after the meat load in both groups in these experimental conditions. The data indicate that the renal tubules contribute to the maintenance of acid-base balance both in healthy subjects and in CRF patients by reabsorbing most of the additional bicarbonate load. The transient, but significant, increase in bicarbonate excretion observed in healthy subjects could be related to the increased tubular load of bicarbonate. In CRF patients, tubular bicarbonate reabsorption was more complete, possibly because of the stimulation of H+ secretion by the mild metabolic acidosis. TA and NH4+ did not participate in tubular compensation of the increased buffer load.