Preservation Of Glomerular Filtration Rate Research Articles

Sex differences in nitrosative stress during renal ischemia

Females suffer a less severe ischemic acute renal failure than males, apparently because of higher nitric oxide (NO) bioavailability and/or lower levels of oxidative stress. Because the renal ischemic injury is associated with outer medullary (OM) endothelial dysfunction, the present study evaluated sex differences in OM changes of NO and peroxynitrite levels (by differential pulse voltammetry and amperometry, respectively) during 45 min of ischemia and 60 min of reperfusion in anesthetized Sprague-Dawley rats. Endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) protein expression and their phosphorylated forms [peNOS(Ser1177) and pnNOS(Ser1417)], 3-nitrotyrosine, reduced sulfhydryl groups (-SH), and glomerular filtration rate (GFR) were also determined. No sex differences were observed in monomeric eNOS and nNOS expression, NO, or 3-nitrotyrosine levels in nonischemic kidneys, but renal -SH content was higher in females. Ischemia increased dimeric/monomeric eNOS and nNOS ratio more in females, but the dimeric phosphorylated peNOS(Ser1177) and pnNOS(Ser1417) forms rose similarly in both sexes, indicating no sex differences in nitric oxide synthase activation. However, NO levels increased more in females than in males (6,406.0 ± 742.5 and 4,058.2 ± 272.35 nmol/l respectively, P < 0.05), together with a lower increase in peroxynitrite current (5.5 ± 0.7 vs. 12.7 ± 1.5 nA, P < 0.05) and 3-nitrotyrosine concentration, (28.7 ± 3.7 vs. 48.7 ± 3.7 nmol/mg protein, P < 0.05) in females than in males and a better preserved GFR after ischemia in females than in males (689.7 ± 135.0 and 221.4 ± 52.5 μl·min(-1)·g kidney wt(-1), P < 0.01). Pretreatment with the antioxidants N-acetyl-L-cysteine or ebselen abolished sex differences in peroxynitrite, nitrotyrosine, and GFR, suggesting that a greater oxidative and nitrosative stress worsens renal damage in males.

CD-NP: An Innovative Designer Natriuretic Peptide Activator of Particulate Guanylyl Cyclase Receptors for Cardiorenal Disease

The natriuretic peptide (NP) family consists of structurally similar, although physiologically distinct, peptides that play an important role in cardiorenal homeostasis. CD-NP is a novel chimeric natriuretic peptide developed by the Mayo Clinic, in which the 15-amino acid COOH-terminus of dendroaspis NP is fused to C-type NP. CD-NP is a dual activator of NP receptors A and B, and therefore, possesses the strong antiproliferative and antifibrotic properties of C-type NP with the potent natriuretic, diuretic, and aldosterone-inhibiting properties of dendroaspis NP. CD-NP has favorable cardiorenal properties when compared to recombinant B-type NP (nesiritide), including preservation of glomerular filtration rate with minimal blood pressure-lowering effects. Thus, CD-NP has emerged as an appealing novel therapeutic strategy for heart failure. The endogenous NP system, the development rationale for CD-NP, as well as in vitro, animal, and human studies and future directions will be reviewed.

Amelioration of metabolic acidosis in patients with low GFR reduced kidney endothelin production and kidney injury, and better preserved GFR

Metabolic acidosis often accompanies low glomerular filtration rate and induces secretion of endothelin, which in turn might mediate kidney injury. Here we tested whether treatment of metabolic acidosis in patients with low glomerular filtration rate reduced the progression of kidney disease. Fifty-nine patients with hypertensive nephropathy and metabolic acidosis had their blood pressure reduced with regimens that included angiotensin-converting enzyme inhibition. Thirty patients were then prescribed sodium citrate, and the remaining 29, unable or unwilling to take sodium citrate, served as controls. All were followed for 24 months with maintenance of their blood pressure reduction. Urine endothelin-1 excretion, a surrogate of kidney endothelin production, and N-acetyl-beta-D-glucosaminidase, a marker of kidney tubulointerstitial injury, were each significantly lower, while the rate of estimated glomerular filtration rate decline was significantly slower. The estimated glomerular filtration rate was statistically higher after 24 months of sodium citrate treatment compared to the control group. Hence it appears that sodium citrate is an effective kidney-protective adjunct to blood pressure reduction and angiotensin-converting enzyme inhibition.

Effect of diet and age on expression of renal NOS isoforms and splicing in female Zucker rats

The underlying hypothesis is that changes in renal oxidative status and nitric oxide synthases (NOS) that occur with progression of nephropathy in obesity‐related Type 2 diabetes mellitus (T2bDM) will be altered in response to an antioxidant‐fortified (AO) diet. Female obese Zucker rats (fa/fa), a model of T2bDM, were studied at 6, 13 and 20 weeks of age, on a regular (REG) or AO diet. Glomerular filtration rate (GFR) was measured and NOS isoforms (n‐neuronal, e‐endothelial and i‐inducible) analyzed with Western blots. The AO diet resulted in better preservation of GFR in 20 week animals. In rats on REG diet eNOS, iNOS and nNOS were highest at 13 weeks, while rats on the AO diet showed significantly decreased levels at this time point. Thus levels of all three isoforms were decreased at 13 weeks in animals on the AO diet compared to animals on the REG diet. This may indicate a protective effect of AO diet at earlier stages of nephropathy. Multiple monomeric splice forms, up to 8 for eNOS and iNOS, and 5 for nNOS were detected; 4–5 dimeric forms were also detected for each isoform. Increased prevalence of active monomers and dimers and detection of a greater number of splice variants were observed in the AO diet groups at 6 and 20 weeks.ConclusionAO diet has a protective effect on renal function in females that may be due, at least in part, to changes in NOS protein expression and activity. Supported by NIH R15 DK073066 to SRI and FVN.

Are Kidneys Not Ischemic in Human Renal Vascular Disease?

Atherosclerotic renal artery stenosis (≥60% lumen occlusion) is a relatively common cause of nephropathy and secondary hypertension, and its frequency increases with age and the presence of cardiovascular disease.1 Renal vascular disease is present in 0.5% to 7.0% of patients over age 65 years, 5.5% of patients with chronic kidney disease, 22.0% of those starting dialysis, 28.0% of those with peripheral vascular disease, 34.0% of elderly patients with congestive heart failure, and up to 50.0% of patients with diffuse atherosclerotic vascular disease.1,2 Clinically, renal vascular disease presents a series of complex challenges, including limited sensitivity of imaging methods for detection, lack of tests that would conclusively establish the functional significance of the stenotic lesion, absence of reliable predictors of the response to revascularization, and uncertainty regarding the optimal method of treatment (medical, angioplasty/stenting, or surgical revascularization). After discovery, progression of renal vascular disease occurs in ≈50%, and 10% of stenotic vessels become occluded within 5 years.1 Progression is characterized initially by renal cortical thinning and loss of renal mass with preservation of glomerular filtration rate and later by further loss of renal mass accompanied by reduced glomerular filtration rate. Traditional pathophysiological concepts of renal vascular disease …

Determinants of urinary albumin excretion reduction in essential hypertension: a long-term follow-up study

The objective of the present study was to assess factors related to long-term changes in urinary albumin excretion (UAE) of nondiabetic microalbuminuric (n = 252) or proteinuric hypertensive individuals (n = 58) in a prospective follow-up. After enrollment, patients were placed on usual care including nonpharmacological treatment and/or treatment with an antihypertensive drug regime to achieve blood pressure < 135/85 mmHg. Periodic UAE measurements were performed until regression or significant reduction (defined when UAE dropped > 50% from the initial values, plus reduction of UAE to < 30 mg/24 h for microalbuminuric patients and < 300 mg/24 h for proteinuric patients). Among the microalbuminuric patients, 113 (44.8%) significantly reduced UAE after a mean follow-up of 18 months (range 12-69 months), 20.3/100 patients per year. Among the proteinuric patients, 29 (50%) significantly reduced UAE after a mean follow-up of 25 months (range 12-51 months), 20.2/100 patients per year. The baseline glomerular filtration rate, diastolic blood pressure and fasting glucose during follow-up were independent factors related to the regression or significant reduction in a Cox proportional hazard model. Regression of UAE was independently related to initial estimated glomerular filtration rate < or = 60 ml/min per 1.73 m (hazard ratio, 0.57; 95% confidence interval, 0.38-0.86; P = 0.001) and DBP > or = 90 mmHg achieved during the follow-up (hazard ratio, 0.57; 95% confidence interval, 0.38-0.86; P = 0.001), even when adjusted for age, gender, body mass index, fasting glucose, presence of treatment at the beginning of the study and treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers during the follow-up. The reduction of urinary albumin excretion was linked to the preserved glomerular filtration rate and to adequate blood pressure control.

Aldosterone synthase (CYP11B2)­344T/C polymorphism and renoprotective response to losartan treatment in diabetic nephropathy

Objective. It has been suggested that an aldosterone synthase gene polymorphism (CYP11B2 ­344T/C) is predictive of the blood pressure lowering effect of angiotensin II receptor blockers in essential hypertension. We investigated whether this polymorphism is predictive of reductions in blood pressure and albuminuria and preservation of glomerular filtration rate (GFR) during short‐term and long‐term treatment with losartan in 57 hypertensive type‐1 diabetic patients with diabetic nephropathy. Material and methods. After a 4‐week washout period, patients received losartan (100 mg o.d.) and were followed for a mean follow‐up of 36 months. At baseline, after 2 and 4 months, and every 6 months thereafter, GFR (51Cr‐EDTA‐clearance), albuminuria and 24‐h blood pressure were determined. The CYP11B2 ­344T/C polymorphism was determined by standard polymerase chain reaction (PCR). Results. The TT, CT and CC genotypes were found in 28 %, 58 % and 14 % of patients, respectively. At baseline albuminuria and blood pressure did not differ between genotype groups. Plasma aldosterone levels (geometric mean (95 % CI)) were similar at baseline: 87 (60–125), 77 (53–112), and 89 (49–161) pg mL−1 and during follow‐up (not significant). After initiation of losartan treatment, comparable mean (SE) reductions in blood pressure and albuminuria were seen in patients with TT, CT and CC genotypes (p >0.6 between groups). After long‐term follow‐up, there was a tendency towards a difference in systolic blood pressure reduction (p = 0.07, one‐way ANOVA), suggesting a poorer response in patients with the CC genotype. No significant difference in rate of decline in GFR (median (range)) was seen between groups (TT, CT, CC): 4.2 (−1.0 to 16.0), 3.2 (−1.6 to 13.8) and 2.6 (−0.1 to 11.0) mL min−1year−1, respectively (p = 0.5). Conclusions. Compared to a previous smaller study of angiotensin II receptor blockade in essential hypertension, we could not confirm that CYP11B2 ­344T/C genotypes contribute towards explaining the observed variability in response to treatment with angiotensin II receptor blockers, which could be due to lack of power.

Juxtaglomerular apparatus T-cell infiltration affects glomerular structure in Type 1 diabetic patients.

Type 1 diabetes is an autoimmune disorder associated with T-cell mediated injury to multiple endocrine tissues. T-cell infiltration of the juxtaglomerular apparatus could be associated with changes in local renin angiotensin system activity and, thus, with changes in the renal microenvironment. We examined the frequency of juxtaglomerular apparatus T-cell infiltration early in Type 1 diabetes and tested whether this is associated with renal structure and function. We classified 89 Type 1 diabetic patients by immunohistochemical analysis as either juxtaglomerular apparatus T-cell positive ( n=37) or T-cell negative ( n=38). Borderline cases ( n=14) were not considered further. T-cell positive patients had a shorter duration of diabetes (6.7+/-2.5 years) than T-cell negative patients (9.2+/-5.0 years, p=0.011) and lower albumin excretion rate, but they had a similar glomerular filtration rate and blood pressure. Renal biopsy morphometric analysis showed similar glomerular basement membrane width and mesangial fractional volume in these two groups. However, glomerular capillary surface density ( p=0.0012) and filtration surface per glomerulus ( p=0.0155) were greater in the T-cell positive patients. Increased filtration surface per glomerulus could be associated with glomerular filtration rate preservation in diabetes. Thus, juxtaglomerular apparatus immunologic injury in Type 1 diabetes patients could delay the clinical consequences of diabetic nephropathy.

Obstructive nephropathy and renal fibrosis: The role of bone morphogenic protein-7 and hepatocyte growth factor: Management of comorbidities in kidney disease in the 21st century: Anemia and bone disease

The nephropathy induced by ureteral obstruction is associated with increased interstitial volume due to matrix deposition, fibroblast differentiation/proliferation, and monocyte infiltration. Recent studies indicate that transforming growth factor-beta (TGF-beta) is linked to renal fibrosis. Tumor necrosis factor (TNF-alpha) has a role in the recruitment of inflammatory cells. We found that infiltration of macrophages of the interstitium in unilateral ureteral obstruction (UUO) occurred as early as four hours after the onset of UUO. Recent studies indicate that a renal tubular development morphogen, bone morphogenetic protein-7 (BMP-7), is effective in preventing the tubulointerstitial nephritis in the setting of obstructive nephropathy. The mechanism of action appears to be preservation of epithelial cell phenotype, inhibition of epithelial-mesenchymal transdifferentiation, and inhibition of injury-induced epithelial cell apoptosis. Hepatocyte growth factor (HGF) also inhibited tubulointerstitial fibrosis. In a treatment protocol in rats with ureteral ligation, BMP-7 restored renal function. The preservation of glomerular filtration rate (GFR) was accompanied by a significant decrease in cortical interstitial volume. In diabetic rats given BMP-7 proteinuria was normalized. In mice with ureteral obstruction, HGF suppressed the expression of TGF-beta and of platelet-derived growth factor. The onset of tubulointerstitial fibrosis was almost completely inhibited by HGF. Both BMP-7 and HGF attenuate the tubulointerstitial fibrosis due to ureteral obstruction. They also increase GFR and renal plasma flow.

Lessons from trials in hypertensive type 2 diabetic patients.

There is incontrovertible evidence that association of type 2 diabetes with hypertension markedly increases the risk of cardiovascular events, death, and nephropathy. In type 2 diabetes, even blood pressure values usually considered below the threshold for hypertension (ie, 140/90 mm Hg) in nondiabetic subjects represent an additional risk of clinical relevance. Evidence that more intensive blood pressure lowering is beneficial in type 2 diabetes over less intensive lowering is also overwhelming. However, most published trials show the need for combination therapy in the great majority of patients, and even with combination therapy it is difficult to attain the expected goal blood pressure, in particular goal systolic blood pressure. It should be recognized that the systolic blood pressure goal of less than 130 mm Hg is a very difficult one to achieve in diabetics. Evidence of the superiority or inferiority of different drug classes is vague and contradictory. Recent evidence concerning angiotensin II receptor antagonists has shown a significant reduction of cardiovascular events, cardiovascular death, and total mortality when losartan was compared with atenolol, but not when irbesartan was compared with amlodipine. If renal endpoints are considered, evidence of the benefit of angiotensin II receptor antagonists in type 2 diabetes is more robust than that available with angiotensin-converting enzyme inhibitors. Primary prevention of development of microalbuminuria seems to be greatly facilitated by strict blood pressure control. However, by attaining normal blood pressure levels (< 130/80 mm Hg), better preservation of glomerular filtration rate does not seem to be insured.

ACE inhibitor intervention in Type 1 diabetes with low grade microalbuminuria.

Several clinical trials have consistently shown that antihypertensive treatment, particularly with angiotensin-converting enzyme inhibitors (ACE-I) reduces albuminuria in Type 1 diabetic patients. More recently, data on the beneficial effects of ACE-I on the preservation of glomerular filtration rate and renal ultrastructure have emerged. However, in general, these trials have recruited a wide spectrum of diabetics, including some patients with severe albuminuria. Thus, the question of the ideal stage at which to instigate what is likely to be lifelong therapy in young people still remains unanswered. Exercise is known to significantly increase both blood pressure (BP) and urinary albumin excretion (UAE), both of which are important determinants of progression of nephropathy in diabetes. Thus, it is possible that exercise may have an adverse effect on diabetic renal disease. The effects of ACE-I on exercise-BP and exercise-UAE in microalbuminuric Type 1 diabetic patients has not been examined in long-term placebo-controlled studies. In the second part of this two-part review, we examine the effects of the ACE-I, lisinopril, 20 mg o.d. for two years, in comparison with placebo, on UAE, 24-hour ambulatory BP, exercise-BP, exercise-UAE and renal haemodynamics in 22 patients with Type 1 diabetes and low-grade microalbuminuria. We further discuss the effects of ACE-I on nephropathy and other complications of diabetes.

Effect of cause and time of dropout on the residual GFR: A comparative analysis of the decline of GFR on dialysis

The decline of residual renal function (RRF) on dialysis has been reported to be slower in peritoneal dialysis (PD) then hemodialysis (HD). However, some clinicians have questioned whether this reported difference might not be caused by selection bias. In particular, if continuous ambulatory PD (CAPD) delivers only marginally adequate therapy as some clinicians speculate, then perhaps those patients on CAPD with low glomerular filtration rate (GFR) are purposefully switched to HD. If true, transferring CAPD patients with low GFR to HD could create a selection bias that very well may account for the differences in GFR between PD and HD. This is particularly problematic if one then censors patients at the time of transfer from PD to HD from analysis (that is, patients are no longer followed in the study once they have switched treatment modalities). When this occurs, the data are said to be informatively censored, a term used by statisticians to describe any kind of systematic bias associated with censored or incomplete data. In particular, informative censoring occurs when patients who die or transfer to another modality very early have an associated lower starting GFR or higher rate of decline of GFR than patients who either complete the study or who die or transfer much later. If patient dropout is indeed related to the rate of decline in GFR and if this relationship differs between PD and HD but is ignored in the analysis, then the results of such analysis may be biased. This article analyzes the decline in GFR among 141 incident dialysis patients (39 HD and 102 PD) undergoing either HD or PD at the University of Missouri-Columbia. The decline in GFR was modeled as a nonlinear function of time, taking into account the possibility that missing values of GFR may be associated with patient dropout (death, transfer to another modality, or transplantation). To safeguard against this possibility, we utilized a conditional nonlinear mixed-effects model. The model was used to fit and compare each patient's GFR data to time adjusting for the patient's treatment modality (HD vs. PD), cause of dropout (death, transfer, transplant, lost to follow-up/study ended), and time to dropout. The model allowed a comparison of the starting GFR and the rate of decline in GFR between PD and HD adjusting for these three factors. The results of our analysis suggest that such informative censoring is independent of treatment modality and that even after correcting for dropout caused by death or transfer to another modality, patients starting on PD have a lower rate of decline in GFR (that is, better preservation of GFR) than patients starting on HD.

Preservation of glomerular filtration rate on dialysis when adjusted for patient dropout

Residual renal function (RRF) plays an important role in dialysis patients. Studies in patients on maintenance dialysis suggest that RRF is better preserved in patients receiving peritoneal dialysis (PD) vis-à-vis those receiving hemodialysis (HD). We speculated that regardless of the patient's type of therapy, the estimate obtained for the rate of decline in glomerular filtration rate (GFR) may be biased because of informative censoring associated with patient dropout. Informative censoring occurs when patients who die or transfer to another modality very early have associated with them a lower starting GFR or a higher rate of decline of GFR than patients who either complete the study or who die or transfer much later. If patient dropout is indeed related to the rate of decline in GFR and if this relationship is ignored in the analysis, then the estimate obtained of the rate of decline in GFR may be biased. In an attempt to determine if there is a relationship between patient dropout and the decline in GFR, we reanalyzed the CANUSA data by modeling GFR as a nonlinear function of time with the rate of decline being exponential. This article highlights the significance of "informative censoring" when studying the decline of RRF on dialysis. The results show that for the CANUSA cohort, the mean initial GFR was significantly lower, and the rate of decline was significantly higher for patients who died or transferred to HD than for patients who were randomly censored or received a transplant. It is important to emphasize that the impact of informative censoring on previous analyses of the decline of RRF between PD versus HD is presently unclear. If bias caused by informative censoring is the same regardless of what therapy a patient is on, then conclusions from previous studies comparing the decline in GFR between PD and HD would still be valid. However, if the magnitude of the bias differs according to therapy, then additional adjustments would be needed to fairly compare the decline in GFR between PD and HD. Because this analysis is restricted to patients on PD, it would be scientifically incorrect to interpret previous studies solely on the basis of the results from this analysis. In any longitudinal study designed to estimate trends in an outcome measured over time, it is important that the analysis of the data takes into account any effect patient dropout may have on the estimated trend. This analysis demonstrates that among PD patients, both the starting GFR and the rate of decline in GFR are associated with patient dropout. Consequently, future studies aimed at estimating the rate of decline in GFR among PD patients should also account for any dependencies between dropout and GFR. Similarly, data analyzing for apparent differences in the rate of decline of GFR between PD and HD should also adjust for possible informative censoring.

Preservation of glomerular filtration rate on dialysis when adjusted for patient dropout

Preservation of glomerular filtration rate on dialysis when adjusted for patient dropout

The use of reduced doses of amifostine to ameliorate nephrotoxicity of cisplatin/ifosfamide-based chemotherapy in patients with solid tumors

This study evaluates the degree of kidney damage during cisplatin/ifosfamide-based combination chemotherapy and its possible prevention by amifostine. Thirty-one patients with solid tumors stratified according to pretreatment were randomized to receive cisplatin/ifosfamide-based chemotherapy with or without amifostine (1000 mg absolute) given as a short infusion prior to cisplatin. Chemotherapy consisted of cisplatin (50 mg/m2), ifosfamide (4 g/m2) and either etoposide (500 mg/m2) (VIP regimen) or paclitaxel (175 mg/m2) (TIP regimen) repeated at 3 weekly intervals. For all patients the glomerular filtration rate (GFR) measured by creatinine clearance, serum creatinine, electrolytes and differential urinary protein excretion were determined prior to, during and after each treatment cycle. A total of 62 cycles of chemotherapy were evaluable. In the amifostine arm the GFR was almost completely maintained after application of two cycles of chemotherapy (121 to 108 ml/min), whereas in the control group a 30% reduction of the GFR (105 to 80 ml/min) was observed. In both groups marked increases of glomerular and tubular marker profiles peaking at day 3 after chemotherapy were found with a nearly complete reversibility of these changes prior to the next chemotherapy cycle. Patients receiving amifostine had a lower degree of hypomagnesemia, as well as a lower urinary excretion of N-acetyl-glucosaminidase and albumin, indicating less tubular damage compared to the control patients. Treatment with 1000 mg amifostine resulted in an almost complete preservation of GFR. This corresponded to a slightly reduced excretion of tubular marker proteins and a lower incidence of hypomagnesemia during chemotherapy in amifostine patients compared to controls. This dose of amifostine may be sufficient for nephroprotection in patients without pre-existing risk factors for renal damage who undergo a restricted number of chemotherapy cycles.

Regulation of glomerular and proximal tubule renin mRNA by chronic changes in dietary NaCl.

Renal adaptations to chronic changes in dietary NaCl and extracellular fluid volume involve both glomerular and tubular mechanisms that result in preservation of glomerular filtration rate and modifications of renal tubular transport to secure external NaCl balance. Although the systemic renin-angiotensin system (RAS) mediates some of these responses, the possible contributions of local glomerular and proximal tubule RASs in these adaptations have not been examined. Thus, in this study, glomeruli and proximal tubules were microdissected from rats adapted to high (4.0%), normal (0.5%), or low (0.01%)-NaCl diets, and renin mRNA was measured using quantitative competitive reverse transcription-polymerase chain reaction. After 4 days of the diets, glomerular renin mRNA abundance was increased 100% by the low-NaCl diet (P < 0.05) and suppressed 50% (P < 0.01) by the high NaCl diet compared with controls. Renin mRNA in proximal tubules was stimulated 230% (P < 0.05) by the low-NaCl diet and tended to be suppressed (68% decrease, not significant) by the high-NaCl diet. When the high-NaCl diet was continued for 2 wk, proximal tubule renin mRNA was suppressed by 89% (P < 0.05). This study provides evidence that glomerular and proximal tubule renin transcript levels are regulated by chronic changes in dietary NaCl, suggesting that local RASs contribute to the renal adaptations in response to chronic alterations in NaCl.

Metabolic Alterations at Different Levels of Renal Function Following Continent Urinary Diversion Through Colonic Segments

Purpose We evaluated the influence of renal function on electrolyte and acid-base homeostasis in patients with colonic reservoirs for urine and the ability of these patients to handle an acute acid load. Materials and Methods The 19 patients studied were divided into 2 groups according to preservation of the glomerular filtration rate at last followup: group 1-well preserved glomerular filtration rate (mean 100 ml. per minute per 1.73 m. 2) with an average followup of 8.5 years and group 2-slight to moderate decrease in glomerular filtration rate (mean 55 ml. per minute per 1.73 m. 2) with a mean followup of 10.5 years. Renal tubular function was evaluated by urinary levels of protein alpha 1-microglobulin. Baseline serum and urine samples were analyzed for metabolic parameters, and baseline arterial blood gas was measured. Immediately thereafter ammonium chloride loading was performed. Results Some difference in acid-base homeostasis was found with slight hyperchloremic metabolic acidosis noted in 4 patients in group 2. Moreover, calcium homeostasis was influenced, with lower levels of ionized calcium noted in group 2. However, no difference was found in the ability of the patients in both groups to handle an acute acid challenge. Conclusions Patients with a glomerular filtration rate of approximately 55 ml. per minute per 1.73 m. 2 have sufficient renal function to compensate for the chronic endogenous acid load noted after urinary diversion and they can also handle an acute acid load adequately. Further studies are necessary to evaluate the long-term effects of a chronic endogenous acid load, for example on bone metabolism, in patients with impaired renal function after urinary intestinal diversion.

A comparison of the effect of ramipril, felodipine and placebo on glomerular filtration rate, albuminuria, blood pressure and vasoactive hormones in chronic glomerulonephritis A randomized, prospective, double-blind, placebo-controlled study over two years

The effects of an ACE-inhibitor (ramipril), a calcium antagonist (felodipine) and placebo on glomerular filtration rate (GFR), urinary albumin/creatinine ratio, blood pressure (BP) and vasoactive hormones were investigated in a randomized, prospective, double-blind, placebo-controlled study of patients with chronic glomerulonephritis and hypertension, with measurements at entrance and after 12 and 24 months. In total, 33 patients were included: 21 completed the study with 7 patients in each group. GFR was measured as 51Cr-EDTA clearance and the vasoactive hormones with radioimmunoassays. The reduction in GFR was significantly more pronounced in the felodipine group (-7 ml/min) than in the ramipril group (0 ml/min) but the same as in the placebo group (-6 ml/min). The urinary albumin/creatinine ratio was significantly more reduced in the ramipril group (-74 mg/mmol) than in the placebo group (-11 mg/mmol), which did not deviate from the felodipine group (-10 mg/mmol). BP was significantly reduced by ramipril and felodipine, but not by placebo. Angiotensin II and aldosterone in plasma increased or tended to increase in the felodipine and placebo groups, but were unchanged in the ramipril group. Endothelin increased only in the placebo group, and vasopressin, atrial natriuretic peptide, and brain natriuretic peptide were not significantly changed in any of the groups. It is concluded that ramipril seems to be superior to felodipine in chronic glomerulonephritis owing to better preservation of GFR.

Blunted cGMP response to agonists and enhanced glomerular cyclic 3′,5′-nucleotide phosphodiesterase activities in experimental congestive heart failure

The natriuretic peptide (NP) and nitric oxide (NO) systems are activated in congestive heart failure (CHF), resulting in increased synthesis of cGMP, which serves as a second messenger for both humoral systems. These two regulatory systems play functional roles in the preservation of glomerular filtration rate (GFR) and sodium excretion in both acute and chronic CHF. A progressive decline in glomerular responsiveness to atrial natriuretic peptide (ANP) characterizes the terminal stage of chronic CHF despite elevation of plasma ANP. Phosphodiesterase isozymes (PDEs) are integral factors in determining cellular content and accumulation of cGMP, and up-regulation of PDE activity could participate in the glomerular resistance to ANP in severe CHF. To date, characterization of possible alteration of glomerular PDE isozyme activities in CHF is unknown, as is the in vitro glomerular response to the nitric oxide-soluble guanylyl cyclase pathway. We, therefore, first determined cGMP generation in response to particulate and soluble guanylyl cyclase activation by ANP and sodium nitroprusside (SNP) in isolated glomeruli from normal (N = 6) and CHF dogs (N = 5) in which CHF was induced by rapid ventricular pacing for 18 to 28 days. Secondly, we explored the presence of major PDE isozymes in glomeruli isolated from the control and CHF dogs. When ANP or SNP (10(-10) to 10(-4) M) were incubated with the suspension of isolated glomeruli, cGMP accumulation was lower by -72 to -96% with ANP and -42 to -77% with SNP in all glomerular medias obtained from CHF compared to controls. PDE hydrolyzing activity of both cAMP and cGMP were higher in the glomerular homogenates obtained from the kidneys of the CHF group (N = 5) compared to those of the control group (N = 5). We conclude that in severe chronic experimental CHF, glomerular cGMP accumulation decreases in response to both ANP and SNP, and CHF is characterized by enhanced cGMP- and cGMP-PDE activities that may participate in glomerular maladaptation to this cardiovascular syndrome.

Section Review; Cardiovascular &amp; Renal: Calcium channel blockers for the treatment of renal disease

Calcium channel blockers are used in the treatment of hypertension because of their ability to decrease peripheral vascular resistance. Recent research has suggested that these drugs also preserve or improve renal function in patients with essential hypertensive renal disease, diabetic renal disease, and in renal transplant recipients with or without cyclosporin therapy. In general, studies in both animal models and humans have demonstrated maintenance or reduction in renal vascular resistance, and preservation or enhancement of renal blood flow and glomerular filtration rate. In addition, calcium channel blockers appear to have a positive effect on renal haemodynamic function in the setting of diabetes mellitus; prospective trials have demonstrated reductions in urinary protein excretion in these patients. Current evidence suggests that calcium channel blockers are well-suited for the treatment of patients with hypertensive disease even in the presence of renal impairment.