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Author(s): Guido Filler [sup.1] [sup.2] [sup.3] [sup.4] , Laura Torres-Canchala [sup.5] , Ajay P. Sharma [sup.1] , Maria E. Díaz González de Ferris [sup.6] , Jaime M. Restrepo [sup.7] [sup.8] [...]

Abstract Transplantation is the best treatment of end-stage renal disease (ESRD); however, organ shortage is a reality. Deceased donor organ donation is inadequate; hence, the number of patients on the [...]

The small GTPase p21 Ras and its downstream effectors play a central role in the control of cell survival and apoptosis. We studied the effects of Ras/ ERK 1/2 signaling inhibition on oxidative damage in cultured renal and endothelial ceils and on renal ischemia-reperfusion injury in the rat. Primary human renal tubular and human endothelial ECV304 cells underwent significant cell death when subjected to oxidative stress. This type of stress induced robustly ERK1/2 and phosphoinositide 3-kinase (PI3-kinase) signaling. Inhibition of Ras/ERK1/2 with a farnesyl transferase inhibitor, chaetomellic acid A (S-FTI), or with PD-98059, an inhibitor of MEK, a kinase upstream ERK1/2, significantly reduced the fraction of dead cells. The inhibitor of the PI3-kinase/Akt pathway, LY-294002, failed to exert a protective effect. We have translated these data in a rat model of renal ischemic injury in vivo. In uninephrectomized animals, anesthetized with pentobarbital sodium (Nembutal, 50 mg/kg ip), 24 h after an acute ischemic renal insult (45-min occlusion of left renal artery) a significant fraction of kidney cells succumbed to cell death resulting in renal failure [glomerular filtration rate (GFR) 0.17 [+ or -] 0.1 vs. 0.90 [+ or -] 0.4 ml*[min.sup.-1]*100g body [wt.sup.-1] in normal rats]. Rats treated with S-FTI maintained the renal function (GFR 0.50 [+ or -] 0.1 ml*[min.sup.-1].100 g body [wt.sup.-1]), and the kidneys showed a significant reduction of tubular necrosis. Reduction of ischemic damage in kidney and tubular cells paralleled Ha-Ras inhibition, assayed by cytosolic translocation of the protein. These data demonstrate that inhibition of farnesylation and consequently of Ras/ERK1/2 signaling significantly reduces acute postischemic renal injury. signal transduction; kidney; endothelium; farnesyl transferase inhibitors

The epithelial [Ca.sup.2+] channels TRPV5 and TRPV6 are the most [Ca.sup.2+]-selective members of the TRP channel superfamily. These channels are the prime target for hormonal control of the active [Ca.sup.2+] flux from the urine space or intestinal lumen to the blood compartment. Insight into their regulation is, therefore, pivotal in our understanding of the (patho)physiology of [Ca.sup.2+] homeostasis. The recent elucidation of TRPV5/ 6-associated proteins has provided new insight into the molecular mechanisms underlying the regulation of these channels. In this review, we describe the various means of TRPV5/6 regulation, the role of channel-associated proteins herein, and the relationship between both processes. Rab11; calbindin; 80KH; BSPRY; Klotho; kidney

In a recent study of transplant outcomes, donor age, cerebrovascular accident as the cause of death (CVA), renal insufficiency (serum creatinine > 1.5 mg/dL), and history of hypertension have been identified as donor factors associated with elevated risk of kidney transplant failure. It is of great interest to know whether there remain other unmeasured donor factors associated with elevated risk of graft failure. In this article we study a sample of 6,024 deceased donor kidney transplants performed in 194 centers from 1995 to 2000. In addition to variation among transplant recipients, there are two other random effects: unmeasured donor and unrecorded center factors (data not available at the physician level). These two random effects are crossed, because the two kidneys from the same donor can be transplanted in different centers. Multivariate frailty models are applied to analyze the data. The likelihood functions of both parametric (e.g., with piecewise constant baseline hazard) and semiparametric multivariate frailty models are shown to be proportional to the likelihood functions of a class of mixed Poisson regression models. The penalized quasi-likelihood method is used as the numerical procedure for these mixed Poisson regression models. Thus we are able to estimate and model crossed random-effects structures for survival analysis. Although about 30% of recipient graft survival rate variation due to donor factors is explained by the measured donor characteristics, the remaining variation among donors in graft survival rate is still statistically significant, suggesting that there may be other unmeasured donor factors associated with a reduced graft survival rate. We also find significant variation of graft failure rates among transplant centers due to unrecorded center factors. Therefore, this study suggests that practice patterns at transplant centers and identification of other donor factors may merit further investigation. KEY WORDS: End-stage renal disease; Mixed Poisson likelihood function; Multivariate survival analysis; Penalized quasi-likelihood; Semiparametric.

Ways to alleviate the shortage of kidney exchange, and improve patient welfare, within the constraints of the existing social and legal environment is considered. The theoretical properties of the proposed kidney exchange is studied and results suggesting that the welfare gains from larger scale exchange would be substantial, both in increased number of feasible live donation transplants, and in improved match quality of transplanted kidney are presented.

Byline: K. Sebekova (1), A. Podracka (2), P. Blazicek (3), D. Syrova (3), A. Heidland (4), R. Schinzel (5) Keywords: Keywords Advanced glycation end products; Carboxymethyllysine; Children; Chronic renal failure; Dialysis; Lipofuscin; Oxidative stress; Renal transplantation Abstract: In adults, advanced glycation end products (AGEs) rise slowly in tissues and circulation during aging, and accumulate at an accelerated rate both in diabetes and chronic renal insufficiency (CRI). We aimed to investigate the pattern of AGE accumulation in children/adolescents with CRI and on renal replacement therapy by dialysis and transplantation. Concentrations of fluorescent AGEs, carboxymethyllysine (CML) and lipofuscin-like substance (LFLS, a marker of lipid peroxidation) were followed. Data were obtained from 11 CRI patients on conservative treatment (age 12.6+-1.7 years, serum creatinine: 205.7+-17.5 Aumol/l), ten patients on renal replacement therapy with dialysis (13.6+-1.7 years, 698.2+-48.9 Aumol/l) and nine patients after kidney transplantation (15.9+-1.1 years, 115.9+-12.0 Aumol/l) and comparison made with the data from 28 healthy controls (11.8+-8.2 years, 44.1+-8.2 Aumol/l). In controls, an age-dependent rise of fluorescent AGE and CML levels was observed. In the CRI group, fluorescent AGEs [0.38+-0.03x10.sup.5 arbitrary units (AU)] and CML (369+-26 ng/ml) concentrations were doubled compared with controls (0.16+-0.03x10.sup.5 AU and 189+-42 ng/ml, respectively) and even higher levels were revealed in dialyzed patients (0.80+-0.05x10.sup.5 AU 650+-94 ng/ml). Successful kidney transplantation significantly reduced but did not normalize fluorescent AGE levels (0.39+-0.03 x10.sup.5 AU), while the decline in CML levels (550+-47 ng/ml) was insignificant. Plasma LFLS was elevated in CRI (19.6+- 1.7 AU) and was even higher in dialyzed children (32.0+-5.3 AU) compared with healthy controls (7.1+- 1.4 AU). Kidney transplantation did not normalize LFLS levels (20.3+-5.3 AU), pointing to persistently enhanced lipid peroxidation. Our study provides the first data on enhanced fluorescent AGEs and CML levels in children/adolescents with CRI and on dialysis. Successful renal transplantation decreased but did not normalize AGE levels, probably because of still-impaired renal function with enhanced oxidative stress, as well as the influence of immunosuppressive therapy. Author Affiliation: (1) Clinic of Pharmacotherapy, Institute of Preventive and Clinical Medicine, 833 01 Bratislava, Slovakia. Sebekova@upkm.sk, SK (2) PJ Safarik Medical School, KoEsice, Slovakia, SK (3) Military Hospital, Bratislava, Slovakia, SK (4) Clinic of Internal Medicine, University of Wurzburg, Wurzburg, Germany, DE (5) Center of Physiological Chemistry I, University of Wurzburg, Wurzburg, Germany, DE Article note: Received: 13 July 2000 / Revised: 8 June 2001 / Accepted: 12 July 2001

The sodium/proton antiporter is responsible for a number of cell housekeeping functions of which one is regulation of cell Ph. An experiment to determine the Na/H antiporter isoform expressed in opossum kidney cells was done. Opossum kidney subclone (OKP) cells show an Na/H exchanger-3 (NHE-3) transcript that encodes an EIPA-resistant Na/H antiporter and is chronically controlled by acid. Applying the degenerate primers based on conserved amino acid sequences in human, rat and rabbit NHE-3, a polymerase chain reaction product was obtained from reverse-transcribed OKP mRNA and applied to screen an OKP cDNA library.

Alterations in Na+ conductance in rabbit cortical collecting duct are a result of the role of oxytocin (OT) in the kidney. Maintained hindrance follows early transient induction of apical Na+ conductance. An enhancement in (Ca2+)i and a cAMP-reliant procedure are paired to the induction of OT receptors in the basolateral membrane to partially control the actions. Lumen-negative transepithelial voltage is enhanced with the early introduction of OT while transepithelial resistance and fractional resistance of the apical membrane are attenuated.

Organic osmolyte betaine transport was observed and studied in rabbit renal brush-border membrane vesicles (BBMV). Na+ betaine and H+-betaine transport is electrogenic in character, as concentrative induction was observed only during occurrence of membrane potential. Chloride presence in the medium had no influence on betaine. L-protine antagonized Na+- and H+- betaine transport, and the H+- sensitive betaine pathway alone was inhibited by glycine. The highest rate of net betaine transport (Jmax) was enhanced by the simultaneous presence of Na+ and H+ gradients. Two unique betaine transport pathways in BBMV were identified. These pathways are defined by their Na+ or H+ sensitivity and their proline and glycine specificity.

The Heymann nephritis antigenic complex (HNAC) comprises a large multinumeric complex that is assembled in the rough endoplasmic reticulum (ER). Tissue fragments made from collagenase-digested 1-day-old rat kidneys were radiolabeled, and gp330 and receptor-associated protein (RAP) were immunoprecipitated with specific antibodies, so as to analyze the biosynthesis and assembly of HNAC and electron microscopy, showed the tubule organization as largely intact. Biosynthesis of a control brush border protein, dipeptidylpeptidase IV (DPPIV), indicated that tubules prepared in this manner are capable of synthesis and post transitional processing of brush border membrane proteins, and hence, are ideal for short-term biosynthetic experiments in vitro.

The [Gamma]-subunit of the Na-K-ATPase is a single-span membrane protein that alters the kinetic properties of the enzyme. It is expressed in the kidney, but our initial observations indicated that it is not present in all nephron segments (Arystarkhova E, Wetzel RK, Asinovski NK, and Sweadner KJ. J Biol Chem 274: 33183-33185, 1999). Here we used triple-label confocal immunofluorescence microscopy in rat kidney with antibodies to Na-KATPase [Alpha]1- and [Gamma]-subunits and nephron segment-specific markers. Na-K-ATPase [Alpha]1-subunit stain was low but unambiguous in proximal segments, moderate in macula densa, connecting tubules, and cortical collecting ducts, high in thick ascending limb and distal convoluted tubules, and nearly undetectable in glomeruli, descending and ascending thin limb, and medullary collecting ducts. The [Gamma]-subunit colocalized at staining levels similar to [Alpha]1-subunit in basolateral membranes in all segments except cortical thick ascending limb and cortical collecting ducts, which had [Alpha]1-subunit but no detectable [Gamma]-subunit stain. Selective [Gamma]-subunit expression may contribute to the variations in Na-K-ATPase properties in different renal segments. immunofluorescence; confocal microscopy; nephron; colocalization; sodium pump

We previously found that p53 upregulation by hypertonicity protected renal inner medullary collecting duct (mIMCD3) cells from apoptosis. The purpose of the present study was to investigate the mechanism by which p53 protects the cells. We now find that hypertonicity (NaCl added to a total of 500 mosmol) inhibits DNA replication and delays [G.sub.1]-S transition as concluded from analysis of cell cycle distributions and bromodeoxyuridine (BrDU) incorporation rates. Lowering of p53 with p53 antisense oligonucleotide attenuated such effects of hypertonicity, resulting in an increased number of apoptotic cells in S phase and cells with [is greater than] 4 N DNA. Results with synchronized cells are similar, showing that cells in the early S phase are more sensitive to hypertonicity. Immunocytochemistry revealed that p53 becomes phosphorylated on [Ser.sup.15] and translocates to the nucleus in S both in isotonic and hypertonic conditions. Caffeine (2 mM) greatly reduces the p53 level and [Ser.sup.15] phosphorylation, followed by a remarkable increase of DNA replication rate, by failure of hypertonicity to inhibit it, and by reduction of cell number during hypertonicity. Finally, inhibition of DNA replication by the DNA polymerase inhibitor aphidicolin significantly improves cell survival, confirming that keeping cells in [G.sub.1] and decreasing the rate of DNA replication is protective and that these actions of p53 most likely are what normally help protect cells against hypertonicity. cell cycle arrest; apoptosis; sodium chloride

Each human kidney contains about 1.3 million minute tubules lined by a continuous layer of epithelial cells. Fluid that is forced out of the blood from specialized capillaries enters these [...]

Living donor transplantation has been performed for 50 years. There is nearly unanimous consent that related living donor transplantation is ethical provided that the donation is based on a free [...]