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B M Brenner

Publications and source records attributed to B M Brenner.

At least 37 records · Page 2Linked to original sources
PubMed2000

Renoprotective benefits of RAS inhibition: from ACEI to angiotensin II antagonists.

In landmark clinical trials, pharmacological inhibition of the renin-angiotensin system (RAS) with angiotensin-converting enzyme inhibitors (ACEIs) attenuated the decline in renal function associated with chronic renal disease (CRD). Hemodynamic and nonhemodynamic effects of angiotensin II (Ang II) attest to its central role in the pathogenesis of CRD. Angiotensin II subtype 1 receptor antagonists (AT1RA) differ from ACEI in their effects on the RAS and on bradykinin metabolism. Elevations in bradykinin levels associated with ACEI and stimulation of angiotensin subtype 2 receptors resulting from AT1RA may produce therapeutic effects unique to each class of drug. Nevertheless, in animal models of CRD, ACEI and AT1RA exert equivalent renoprotection, implying that their renoprotective effects result primarily from inhibition of Ang II-mediated stimulation of angiotensin subtype 1 receptors. Clinical data comparing ACEI and AT1RA therapy in renal disease are limited to short-term studies, which indicate that AT1RAs have equivalent effects to ACEI on the major determinants of CRD progression, namely blood pressure and proteinuria. AT1RAs were well tolerated, with side-effect profiles similar to placebo. Taken together, available evidence suggests that AT1RAs will share the renoprotective properties of ACEI in human CRD. Nevertheless, the results of long-term clinical trials are required before AT1RA can be recommended as an alternative to ACEI in renoprotective therapy.

Angiotensin II↗
PubMed2000

Renal allograft protection with losartan in Fisher-->Lewis rats: hemodynamics, macrophages, and cytokines.

BACKGROUND: We sought to assess the effects of angiotensin receptor blockade on glomerular hypertension, macrophage recruitment, and cytokine expression, all of which contribute to the development of chronic graft injury in this model. METHODS: The effects of treatment with the specific angiotensin II type 1 (AT1) receptor antagonist, losartan, were assessed over 24 weeks in F344-->LEW rats (LOS, N = 9) versus vehicle-treated F344-->LEW controls (CON, N = 9). RESULTS: UprotV rose progressively in CON (from 7.0 +/- 2.9 to 41 +/- 17 mg/day at 24 wk) but remained at baseline in LOS (4.2 +/- 0.6 to 9.4 +/- 1.3 mg/day, P < 0.05 vs. CON). Glomerular capillary pressure (PGC) was increased in CON (71 +/- 1 mm Hg at week 20), but remained within the normal range in LOS rats (54 +/- 2 mm Hg, P < 0.05). Glomerulosclerosis averaged 0.3 +/- 0.2% in LOS versus 4 +/- 2% in CON rats (P < 0.05). Tubulointerstitial injury was minimal in both LOS and CON rats (+). The overexpression of renal cortical cytokine mRNA levels for the monocyte chemoattractants, monocyte chemoattractant protein-1 (MCP-1) and RANTES, as well as interleukin-1, inducible nitric oxide synthase, and transforming growth factor-beta, assessed by competitive reverse transcription-polymerase chain reaction, was suppressed in LOS versus CON rats at 20 weeks. Macrophage and T-cell numbers were decreased, and MCP-1, RANTES, and intercellular adhesion molecule-1 staining in the graft, identified by immunohistochemistry, were attenuated in LOS versus CON rats. CONCLUSIONS: The renoprotective effects of losartan in F344-->LEW rats were associated with lowered PGC, inhibition of macrophage chemoattractants and recruitment, and suppression of macrophage-associated cytokines at 20 weeks. These findings suggest that chronic allograft injury in F344-->LEW rats is, to a large extent, mediated by angiotensin II-dependent mechanisms and that these involve glomerular hemodynamics, macrophages, and macrophage-associated cytokines.

Angiotensin Receptor Antagonists↗
PubMed2000

Proinflammatory gene expression and macrophage recruitment in the rat remnant kidney.

BACKGROUND: Macrophage (Mphi) infiltration may contribute to chronic renal injury. We therefore sought to examine the expression of genes associated with Mphi recruitment in the rat remnant kidney model. METHODS: Male Munich Wistar rats underwent 5/6 nephrectomy or sham operation (SHM, N = 18) and received no treatment (VEH, N = 18), enalapril 100 mg/L (ENA, N = 18), or candesartan 70 mg/L (CSN, N = 24) in drinking water. Competitive, quantitative reverse transcription-polymerase chain reaction was used to determine renal cortex mRNA levels for cell adhesion molecules vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), the Mphi chemoattractant monocyte chemoattractant protein-1 (MCP-1), Mphi products interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), and the profibrotic cytokine transforming growth factor-beta1 (TGF-beta1), at intervals post-nephrectomy. RESULTS: Glomerular and interstitial Mphi infiltration in VEH rats was associated with an early (4 week) and sustained rise in MCP-1 and TGF-beta1 mRNA levels. Progressive increases in ICAM-1, VCAM-1, IL-1beta, and TNF-alpha expression followed at 8 and 12 weeks. Immunostaining in VEH rats localized TGF-beta1 to glomeruli, tubules, and interstitium; MCP-1 to tubules and interstitial cells; ICAM-1 to glomeruli; and IL-1beta and TNF-alpha to tubules and interstitial cells. At 12 weeks, both treatments normalized systolic blood pressure (ENA, 105 +/- 6; CSN, 97 +/- 3 mm Hg) and the urinary protein excretion rate (ENA, 8.4 +/- 0.9; CSN, 5.7 +/- 0.8 mg/day), prevented renal injury (focal and segmental glomerulosclerosis: ENA, 3.3 +/- 0.9; CSN, 1.3 +/- 0.4%), and suppressed Mphi infiltration and cytokine expression (with the exception of TNF-alpha) to near SHM levels. CONCLUSIONS: These findings support the hypothesis that the coordinated up-regulation of several molecules regulating Mphi recruitment and activation is a fundamental response to renal mass ablation and is dependent on an intact renin-angiotensin system. We speculate that these responses may play a role in the pathogenesis of the ensuing glomerulosclerosis and tubulointerstitial fibrosis.

Animals↗
PubMed2000

The losartan renal protection study--rationale, study design and baseline characteristics of RENAAL (Reduction of Endpoints in NIDDM with the Angiotensin II Antagonist Losartan).

The RENAAL Study is a double-blind, placebo-controlled trial to evaluate the renal protective effects of losartan in Type 2 diabetic patients with nephropathy. The study has enrolled 1513 patients and is expected to continue for 3.5 years after the last patient has been entered. Eligible patients must have a urinary albumin:creatinine ratio of at least 300 mg/g and serum creatinine between 1.3 to 3.0 mg/dL. Eligible hypertensive or normotensive patients are randomised to receive either losartan or placebo, in addition to their existing antihypertensive therapy. Medications that block angiotensin production or action, are excluded. The primary endpoint is a composite of the time to first event of doubling of serum creatinine, end-stage renal disease, or death; secondary endpoints include cardiovascular events, progression of renal disease, and changes in proteinuria; tertiary endpoints include quality of life, healthcare resource utilisation, and amputations. Patients include Caucasians (48.6%), Blacks (15.2%), Asians (16.7%), and Hispanics (18.2%). Baseline urinary albumin:creatinine ratio and serum creatinine levels average 1867 mg/g and 1.9 mg/dL, respectively. Mean systolic and diastolic blood pressures are 153 and 82 mmHg, respectively. RENAAL will document whether blockade of the AII receptor with losartan produces clinical benefits in patients with Type 2 diabetes and nephropathy.

Aged↗
PubMed2000

Increased gene expression of adrenomedullin and adrenomedullin-receptor complexes, receptor-activity modifying protein (RAMP)2 and calcitonin-receptor-like receptor (CRLR) in the hearts of rats with congestive heart failure.

Adrenomedullin is a vasodilator peptide produced in various organs, including heart and kidney. A novel adrenomedullin receptor complex has recently been identified, namely the calcitonin receptor-like receptor (CRLR) and receptor-activity modifying protein (RAMP) 2. In the present study, we have examined gene expression of RAMP2, CRLR and adrenomedullin in hearts and kidneys of rats with congestive heart failure caused by coronary artery ligation. Partial cloning was performed to determine the rat RAMP2 nucleotide sequence. Messenger RNA levels were then determined using competitive, quantitative reverse transcription-PCR techniques. Significantly increased expression levels (means+/-S.E.) of RAMP2, CRLR and adrenomedullin mRNA were found in the atrium (1.8+/-0.2-fold, 1. 8+/-0.2-fold and 2.1+/-0.1-fold, respectively, compared with sham operated rats) and in the ventricle (1.4+/-0.1-fold, 1.3+/-0.03-fold and 3.0+/-0.5-fold respectively). On the other hand, expression levels of RAMP2, CRLR and adrenomedullin mRNAs were not significantly changed in the kidney. These findings suggest potential roles of locally-produced and locally-acting adrenomedullin in the failing heart.

Adrenal Medulla↗
PubMed1999

ACE-I vs angiotensin II receptor antagonists: prevention of renal injury in chronic rat models.

There is now abundant evidence that treatment with angiotensin-converting enzyme inhibitors (ACE-I) ameliorates the progression of chronic renal disease. Attention has therefore focused on the role of the renin angiotensin-aldosterone (RAA) system in mediating the development of progressive glomerulosclerosis and angiotensin II (Ang II) has been implicated in several processes thought to be important in the pathogenesis of this entity. Conversely, ACE is also known to catalyse the breakdown of bradykinin. Thus, ACE-I treatment results in elevated bradykinin levels which may cause selective efferent arteriolar dilatation, suggesting an alternative explanation for the beneficial effects of this class of drugs in chronic renal disease. The development of specific angiotensin type 1 receptor antagonists (AT1RA) has provided a means of testing the relative importance of these two mechanisms. In addition, AT1RAs differ from ACE-I in their effect on the RAA system in other aspects which may represent therapeutic advantages. This paper reviews studies which have compared ACE-I and AT1RAs in several rat models of chronic renal disease. Most have found similar beneficial effects including amelioration of proteinuria and glomerulosclerosis, which suggests that the effects of ACE-I are due to a reduction in Ang II activity and not due to increased levels of bradykinin. One long-term study has suggested greater renal protection with candesartan than with enalapril. However, conclusions as regards the relative efficacy of these two groups of agents in ameliorating the progression of chronic renal disease await the results of further long-term studies.

Angiotensin Receptor Antagonists↗
PubMed1999

Renin-angiotensin blockade lowers MCP-1 expression in diabetic rats.

BACKGROUND: Glomerular macrophage accumulation in diabetes implicates monocyte recruitment mechanisms in the pathogenesis of diabetic nephropathy. To test the hypothesis that overexpression of monocyte chemoattractant protein-1 (MCP-1), a monocyte chemoattractant, is attenuated by renin-angiotensin system (RAS) inhibition, we assessed expression of genes regulating monocyte transmigration in the glomeruli of diabetic rats. METHODS: Competitive reverse transcription-polymerase chain reaction (RT-PCR) was used to semiquantitate mRNA expression in glomeruli harvested by sieving at serial intervals after the induction of diabetes by streptozotocin in Munich-Wistar rats. Although subject to limitations, competitive RT-PCR provides an objective measure suited to the minute quantities of RNA extractable from glomerular isolates. RESULTS: Time-dependent elevation of MCP-1 expression was dramatically suppressed by treatment with the angiotensin-converting enzyme inhibitor enalapril or the AT1 receptor antagonist candesartan, and was closely associated with effects on proteinuria and glomerular macrophage number. By contrast, no sustained suppression of the cell adhesion molecules intercellular adhesion molecule-1 or vascular cell adhesion molecule-1 or the classic MCP-1 stimulators tumor necrosis factor-alpha or interleukin-1beta followed RAS inhibition, and suppression of transforming growth factor-beta1 expression was transient. CONCLUSION: These data suggest that glomerular macrophage recruitment in experimental diabetes is largely determined by angiotensin-stimulated MCP-1 expression. We conclude that the RAS is an important regulator of local MCP-1 expression, either directly or through glomerular hemodynamic effects, and that our data strongly implicate macrophage recruitment and activation in the pathogenesis of early diabetic glomerular injury.

Angiotensin Receptor Antagonists↗
PubMed1999

Early experience with dual kidney transplantation in adults using expanded donor criteria. Double Kidney Transplant Group (DKG).

Dual transplant of marginal kidneys otherwise not considered for single transplant may give access to an expanded pool of cadaveric organs without exposing recipients to the drawbacks of a limited nephron mass supply. This prospective, case-control study compares adverse events and graft outcome in 24 recipients of two marginal kidneys from donors who were >60 yr old or who had diabetes, hypertension, or non-nephrotic proteinuria (cases), with that of 48 age- and gender-matched control subjects who received single ideal grafts at the same center and were given the same immunosuppressive therapy. Marginal kidneys with no macroscopic abnormalities were selected for the double transplant on the basis of a predefined score of histologic damage. Six-month patient and kidney survival was 100% with both of the procedures. Incidence (20.8% versus 20.8%) and median (range) duration of posttransplant anuria (5 [2 to 12] versus 7 [2 to 13] days) were comparable in cases and control subjects, respectively. Time to normal serum creatinine and mean serum creatinine values at each time visit were comparable as well, but with significantly lower levels in cases compared with control subjects from month 2 to last follow-up (1.56 +/- 0.65 versus 1.74 +/- 0.73 mg/dl, P = 0.04). Diastolic BP values averaged during the entire posttransplant period were significantly lower in cases than in control subjects (83.2 +/- 11.5 versus 85.1 +/- 12.5 mmHg, respectively, P = 0.008). Donor/recipient body weight ratio was the only covariate significantly associated at univariate (P = 0.002) and multivariate (P = 0.001) analysis with last available serum creatinine concentrations. Incidence of acute allograft rejections (20.8% versus 18.8%) and of major surgical complications was comparable in the two groups. No renal artery or vein thrombosis was reported in either group. Dual transplants of marginal kidneys are as safe and tolerated as single transplants, and possibly offer an improved filtration power without exposing the recipient to enhanced risk of delayed renal function recovery, acute allograft rejection, or major surgical complications.

Adult↗
PubMed1999

Renal function in high-output heart failure in rats: role of endogenous natriuretic peptides.

The physiologic and pathophysiologic importance of natriuretic peptides (NP) has been imperfectly defined. The diminished renal responses to exogenous atrial NP in heart failure have led to the perception that the endogenous NP system might be less effective and thus contribute to renal sodium retention in heart failure. This study tests the hypothesis that in experimental heart failure, the renal responses to an acute volume load are still dependent on the NP system. The specific antagonist HS-142-1 was used to block the effects of NP in a model of high-output heart failure induced by an aortocaval shunt. Plasma cGMP levels and renal cGMP excretion were significantly lower in shunted and sham-operated rats receiving HS-142-1, compared with vehicle-treated controls, indicating effective blockade of guanylate cyclase-coupled receptors. Baseline sodium excretion and urine flow rate were lower in HS-142-1-treated sham-operated rats (15.2+/-1.1 microl/min versus 27.5+/-3.1 microl/min with vehicle, P < 0.001) and in HS-142-1-treated shunted rats (8.1+/-1.3 microl/min versus 19.9+/-2.3 microl/min with vehicle, P < 0.001). After an acute volume load, the diuretic and natriuretic responses were attenuated by HS-142-1 in control and shunted rats. The renal responses were reduced by HS-142-1 to a significantly greater extent in shunted rats than in control rats. HS-142-1 did not induce any significant systemic hemodynamic changes in either group, nor did it alter renal blood flow. However, the GFR in HS-142-1-treated shunted rats was lower than that in vehicle-treated shunted rats, both at baseline (0.6+/-0.3 ml/min versus 2.1+/-0.4 ml/min with vehicle, P < 0.05) and after an acute volume load (1.2+/-0.4 ml/min versus 2.6+/-0.4 ml/min with vehicle, P = 0.01), whereas no such effect was observed in control rats. These data indicate that the maintenance of basal renal function and the responses to acute volume loading are dependent on the NP system. The NP seem to be of particular importance for the maintenance of GFR in this model of experimental heart failure. These observations provide new insights into the importance of the renal NP system in heart failure.

Analysis of Variance↗
PubMed1998

The effect of dietary vitamin D3 on the intracellular calcium gradient in mammalian colonic crypts.

A physiological gradient in intracellular calcium ([Ca2+]i) has been hypothesized to exist along the colonic crypt base-mouth axis, which may be involved in the regulation of colonocyte proliferation, differentiation and apoptosis. In addition [Ca2+]i may be modulated by dietary vitamin D3 which is thought to be protective against colorectal cancer. CF1 mice were maintained for 6 weeks on a defined diet containing either high or low vitamin D3. A colonic crypt base-mouth [Ca2+]i gradient of 201 +/- 79 nM (mean +/- SEM, P < 0.05) was observed in animals maintained on a high vitamin D3 diet and was abolished in mice maintained on a low vitamin D3 diet. The [Ca2+]i gradient was independent of extracellular calcium and elevated levels of [Ca2+]i observed in the basal regions of the crypt in animals maintained on low levels of vitamin D3 were also associated with an increase in intracellular calcium stores. Therefore, a [Ca2+]i gradient exists in colonic crypts and is dependent on dietary vitamin D3.

Animals↗
PubMed1998

Toward global advancement of medicine: the International Society of Nephrology experience.

BACKGROUND: Since its foundation in 1960, the International Society of Nephrology (ISN) has pursued the worldwide advancement of education, science and patient care in nephrology. This goal was achieved by means of the Society's journal and the organization of international congresses and symposia. In order to better reach its colleagues and patients in economically less developed countries, the ISN expanded its activities as of 1980 by a large number of specific programs aimed at these regions. METHODS: The first phase of activities included teaching programs, fellowship and visiting scholar programs, and the provision of travel grants to enhance accessibility to the ISN congresses. A second phase consisted of the creation of a library enhancement program, a commission on acute renal failure and--to improve the organization and efficiency--a central commission on global advancement of nephrology (COMGAN). Currently, a third phase has been entered in which all activities have been intensified: (1) under the guidance of COMGAN, supported by a large number of teaching programs and fact finding missions; (2) by establishing a renal sister program; and (3) by initiating commissions on informatics and on clinical trials. RESULTS: As a result, the ISN has reached most parts of the world, previously deprived of contact with renal science and renal patient care. The fellowship program now counts 160 fellows, who spend one or two years in training. The library enhancement program reaches 218 institutions worldwide. ISN membership has soared over the past two years with over 2,500 new members, mostly in the developing countries. They receive Kidney International and other relevant forms of information. Thus far, 135 pairs of renal units in developing and developed countries have been linked for support on a more continuous basis. ISN-sponsored congresses, symposia, and courses are being held in increasing numbers in the developing world. In many of its activities, the ISN closely collaborates with sister organizations, which also contribute financially. In total, the ISN spends annually over $1 million US from its own budget on the programs described above. CONCLUSION: The various programs and initiatives are proving helpful in advancing renal medicine in areas in need. Expansion into supporting similar programs within other medical subspecialties is being explored.

Humans↗
PubMed1998

Current strategies for retarding progression of renal disease.

Physiological insights gained in the 1980s into mechanisms of disease progression in experimental chronic nephropathies established the basis for therapeutic interventions to retard the progression of chronic renal disease in humans. In the 1990s, several large-scale clinical trials have confirmed the renoprotective effects of angiotensin-converting enzyme inhibitors in diabetic and nondiabetic nephropathies. Other studies have afforded strong support for the efficacy of dietary protein restriction in certain settings and underscored the importance of blood pressure control in proteinuric individuals. These interventions form the core of current strategies designed to preserve kidney function in patients with chronic renal disease.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Effects of combination therapy with enalapril and losartan on the rate of progression of renal injury in rats with 5/6 renal mass ablation.

Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor antagonists (AT1RA) slow the rate of progression of experimental renal disease. Although the end result of both classes of drugs is to block the renin-angiotensin system (RAS), ACEI and AT1RA act at different sites in the RAS cascade. The aim of this study was to compare the effects of an ACEI (enalapril) and AT1RA (losartan), alone or in combination, in slowing the progression of experimental renal disease in a model of reduced renal mass. Two weeks after 5/6 renal ablation, rats were divided into five groups matched for body weight, systolic BP (SBP), and urinary protein excretion rate (UprotV). The effects on SBP and UprotV of treatment with 25 and 40 mg/L enalapril (groups I and II; both n = 7), 180 mg/L losartan (group III, n = 8), or a combination of enalapril (25 mg/L) + losartan (180 mg/L) (group IV, n = 9) versus vehicle (group V, n = 9) were studied for 12 wk. Remnant kidneys were then assessed histologically for evidence of focal and segmental glomerulosclerosis and hyalinosis (FSGS), and interstitial fibrosis. There were no significant differences (NSD) in body weight among the groups at any time. Combination therapy reduced SBP (122 +/- 8 mmHg) significantly at 12 wk to levels similar to losartan (127 +/- 3 mmHg) or enalapril (40 mg/L) alone (124 +/- 5 mmHg) (P < 0.05 versus vehicle controls). With equivalent antihypertensive effects, no differences in frequency of FSGS were discerned among the treatment groups (groups II through IV; F = 1.7, NSD). Tubulointerstitial injury scores followed a similar pattern. BP was highly correlated with the extent of FSGS, both among individual rats (r = 0.68, P = 0.05) and the group means (r = 0.99, P = 0.001). We conclude that the renoprotective effects of enalapril, losartan, or combination therapy are similar in this model over the 12 wk of the study, and are closely related to the magnitude of their antihypertensive effects.

Analysis of Variance↗
PubMed1998

Progressive glomerular injury in the MWF rat is predicted by inborn nephron deficit.

It has been suggested that a reduced number of nephrons may predispose to systemic hypertension and glomerular injury. Compensatory hemodynamic changes, due to a low number of glomeruli, might be responsible for glomerular functional and structural changes. It is difficult to evaluate this hypothesis in humans because of limitations in estimating the number of nephrons in the living kidney. The aim of the present study was to estimate nephron number, single glomerular hemodynamics, and glomerular volume in male and female MWF rats, a strain that spontaneously develops systemic hypertension, proteinuria, and glomerulosclerosis. Male and female Wistar rats were used as controls. At 12 to 14 wk of age, male MWF rats developed proteinuria, whereas female MWF and Wistar rats showed normal urinary protein excretion rate. Glomerular number was significantly reduced in male and female MWF rats (13,690+/-1,489 and 12,855+/-1,781 gl/ kidney, respectively) compared with Wistar rats (26,955+/-2,171 and 27,166+/-1,754 gl/kidney, respectively). The mean number of nephrons per unit of body weight was also lower in MWF males (88+/-10) compared with MWF females (139+/-20) and compared with male and female Wistar animals (142+/-14 and 221+/-22 gl/g body wt). Whole-kidney hemodynamic parameters and the number of nephrons were used to calculate single-nephron filtration rate and plasma flow. Both measures were markedly elevated in male MWF rats relative to values obtained in the other three groups. Similarly, glomerular volume was significantly greater in MWF males than in other animals. These results suggest that an inborn deficit of nephrons may be responsible for spontaneous development of later-in-life hypertension and renal dysfunction. The data also indicate the need to investigate the role of this potential pathogenetic factor for human hypertension and kidney disease in humans.

Animals↗
PubMed1998

Upregulation of atrial natriuretic peptide gene expression in remnant kidney of rats with reduced renal mass.

Atrial natriuretic peptide (ANP) is synthesized in the kidney but its physiologic significance there is unclear. To determine whether renal expression of the ANP gene is regulated, renal ANP mRNA expression was assessed in remnant kidneys after 5/6 nephrectomy in Munich-Wistar rats. In normal sodium intake groups, ANP mRNA expression in the remnant kidney was significantly increased by 5.0 +/- 0.8-fold (n = 7, mean +/- SEM) at 4 d when compared with sham-operated controls (n = 6, all sham-operated groups) (*P < 0.001 by Scheffe's test) and by 28.3 +/- 5.1-fold at 14 d. This latter response was markedly diminished to 7.6 +/- 2.1-fold (n = 7, versus sham) in rats maintained on a low sodium diet. At 4 d, on the other hand, no significant downregulation was observed with dietary sodium restriction. Because natriuretic peptides have previously been shown by us to play a major role in the adaptive responses of remnant nephrons to renal mass ablation, these data suggest that ANP of renal origin may contribute to the overall mechanism for enhancing sodium excretion in the face of declining nephron number.

Analysis of Variance↗
PubMed1998

Renal effects of an acute NaCl load in chronic nitric oxide blockade-induced hypertensive rats.

Nitric oxide (NO) controls blood pressure and plays a role in the water and sodium handling by the kidneys. Inhibition of NO synthesis with competitive L-arginine analogues leads to increased renal vascular resistance and raised systemic and glomerular blood pressure. The effects of chronic NO-synthesis inhibition by N(G)-nitro L-arginine methyl-esther (L-NAME) in the disposal of an acute NaCl load are studied on fourteen male Munich-Wistar rats. Eight of which were given L-NAME (100 mg/L) in the drinking water for 21 days. Six control rats differed only in not receiving L-NAME. As expected, significant hypertension and a marked renal vasoconstriction were accompanied by a decline in renal plasma flow, without changes in glomerular filtration rate, with filtration fraction thus being increased in the NO-blocked rats. In the basal state there was no significant reduction of sodium urinary excretion in the L-NAME treated rats. Both groups of rats elicited an increase in urinary sodium excretion after the NaCl load which was initially more evident and longer in the L-NAME treated group. The ratio of Na+ excreted to Na+ infused was similar between the groups. This observation suggests that in this model of chronic inhibited NO rats, the disposal of an acute sodium load is reached. The existence of a delayed mechanism in renal excretion of Na+ by the chronic NO-blocked rats could be suggested.

Animals↗
PubMed1997

Nephron mass modulates the hemodynamic, cellular, and molecular response of the rat renal allograft.

Functioning nephron mass has recently been implicated as a risk factor for development of chronic "rejection" of kidney allografts. Reductions in nephron number below 50% may induce glomerular hypertension and hyperfiltration in surviving units, which in turn lead to graft injury. In the present study, which extends and amplifies our previous investigations, cellular and molecular characteristics of single allografts from F344 donors in bilaterally nephrectomized LEW recipients, our standard experimental model of chronic renal allograft dysfunction, were compared with allografts from recipients where total renal mass was reduced (by ligating branches of the graft renal artery) or restored to normal levels by transplanting or retaining a second kidney. Our findings in this study confirm that progressive proteinuria and structural injury in recipients of single allografts were accentuated in grafts with reduced mass but virtually absent in rats with increased kidney mass. A striking observation was that patterns of cell surface molecule expression, cellular infiltration, and expression of all T cell- and macrophage-associated products studied were all markedly modulated by changes in renal mass. Moreover, several molecules that are up-regulated before evidence of graft injury are down-regulated by providing increased renal mass. These data show that the quantity of functioning renal mass is not only an important independent determinant of the tempo and intensity of chronic renal allograft failure, but also a potent modulator of fundamental cellular and molecular components of a complex process. This phenomenon involves antigen-dependent and antigen-independent elements that ultimately result in chronic allograft failure.

Animals↗