Hepatitis C virus in chronic dialysis patients.

Since the cloning of hepatitis C virus (HCV), numerous serologic and virologic tests for detecting HCV infection have been developed and implemented in clinical practice. As a result, significant advances have been made in the study of HCV infection in patients with end-stage kidney disease. Patients on hemodialysis have a higher incidence and prevalence of HCV infection than the general population. In addition, HCV infection affects adversely survival among patients with end-stage kidney disease. Risk factors for HCV infection in dialysis patients include number of blood transfusions, duration of hemodialysis, mode of dialysis, prevalence of HCV infection in the dialysis unit, previous organ transplantation, intravenous drug use, male gender, older age and nosocomial transmission of HCV in hemodialysis units that can occur due to breakdown in standard infection control practices, physical proximity to an infected patient, cross-infection through dialysis machines, disrupted integrity of dialyzer membrane or dialyzer reprocessing. Suggested strategies to control HCV transmission in hemodialysis units include strict adherence to universal precautions, careful attention to hygiene, sterilization of dialysis machines and routine serologic testing and surveillance for HCV infection. Antiviral therapy with interferon alpha is recommended for selected categories of HCV-infected hemodialysis patients and kidney transplant candidates.

Transmission of viral hepatitis by kidney transplantation: donor evaluation and transplant policies (Part 1: hepatitis B virus).

This two-part article discusses serologic testing of prospective donors for viral hepatitis B and C, as part of the comprehensive donor evaluation, and reviews the current policies and practices aimed at preventing donor-to-recipient transmission of hepatitis B and C viruses (HBV, HBC). This first part of the review discusses HBV. Organs procured from HBV-infected donors can transmit the virus to their recipients. Because infections with HBV have been associated with increased morbidity and mortality among renal transplant recipients, it is important to prevent HBV transmission with renal transplantation. Routine serologic evaluation of prospective organ donors for markers of HBV infection includes testing for hepatitis B surface antigen (HBsAg), anti-hepatitis B surface antigen antibody (HBsAb), and antibody to hepatitis B core antigen (anti-HBc). The risk of HBV transmission with kidney transplantation is a function of the serologic status of both donor and recipient. Knowledge of this risk is essential for the rational use of kidney allografts. HBsAg-positive donors are at high risk of transmitting HBV infection to their organ recipients, particularly if these donors are concurrently positive for hepatitis B e antigen (HBeAg). Kidneys from donors with isolated presence of HBsAb are unlikely to transmit HBV infection to their recipients. The risk of HBV transmission with the use of kidneys from IgG anti-HBc-positive, HBsAg-negative donors is low. Kidneys from donors negative for both HBcAg and anti-HBc are at low-to-negligible or no risk of transmitting HBV to their recipients. Under certain conditions, kidneys from HBV-infected donors can be safely used and thus prevent unnecessary discarding of organs. Kidneys from HBsAg-positive donors, who are negative for HBeAg, carry no risk or only minimal risk of transmitting HBV infection to their recipients if these recipients are immune to HBV or HBsAg-positive. However, the safety of these policies deserves further evaluation.

Transmission of viral hepatitis by kidney transplantation: donor evaluation and transplant policies (Part 2: hepatitis C virus).

This two-part article discusses serologic testing of prospective donors for viral hepatitis B and C as part of the comprehensive donor evaluation and reviews of the current policies and practices aimed at preventing donor-to-recipient transmission of hepatitis B and C viruses (HBV, HBC). This second part of the review discusses HCV. Organs procured from HCV-infected donors can transmit the virus to their recipients. Because a number of studies have associated infections with HCV with increased morbidity and mortality among renal transplant recipients, it is important to prevent HCV transmission with renal transplantation. The majority of organ procurement organizations (OPOs) perform routine screening of organ donors for antibodies to HCV (anti-HCV). The prevalence of HCV infection among cadaver organ donors, ascertained based on a positive anti-HCV test by ELISA2, varies worldwide between 1.08% and 11.8%. The use of kidneys from donors negative for anti-HCV by ELISA2 carries negligible or no risk of transmitting HCV infection. The use of organs from anti-HCV-positive donors has been restricted to life-saving transplants (heart, liver or lung) by the majority of OPOs worldwide. However, discarding kidneys from all anti-HCV positive donors would lead to unnecessary waste of organs because not all anti-HCV positive donors are infectious. Recently, the policy of unconditional restriction on the use of kidneys from anti-HCV positive donors has been challenged, and transplantation of organs from anti-HCV-positive donors into anti-HCV-positive recipients has been found to be safe. An even better alternative might be a policy of transplanting kidneys from anti-HCV-positive donors only in HCV RNA-positive recipients. However, until more data become available, these two strategies remain experimental treatments.

Routine serologic testing for hepatitis C virus infection should be instituted among dialysis patients.

Since the cloning of hepatitis C virus (HCV), a number of serologic and virologic tests for detecting infections with this virus have been made available for clinical practice. This led to the recognition of HCV as a major health hazard in hemodialysis (HD) centers. Yet the nephrology community has not been offered explicit recommendations about routine serologic testing for HCV of dialysis patients and consequently has remained unclear and divided about the utility of this testing. This review presents evidence in support of instituting routine serologic testing for HCV among dialysis patients. It concludes that because of the peculiar features of HCV infection in HD patients, serologic testing for HCV is the only means for unequivocal diagnosis of hepatitis C and an irreplaceable instrument for monitoring the incidence and the prevalence of the infection in this population. Serologic surveillance for HCV infection is crucial for identifying the association of new cases of HCV infection with potential risk factors for HCV transmission, particularly nosocomial, that can be modified in a way to prevent further dissemination of the virus. Data collected from routine serologic testing for HCV will undoubtedly improve our understanding of the epidemiology of HCV in the dialysis population and will provide a strong foundation for developing preventive measures and infection control strategies that are highly effective in controlling HCV infection. Routine serologic testing for HCV is also of direct benefit to the individual patient since establishing the HCV serologic status of each patient is important for optimizing patient care.

Hepatitis C virus mixed genotype infection in patients on haemodialysis.

Hepatitis C virus (HCV) has been classified into different genotypes/subtypes with demonstrated clinical implications. Whether there is biological difference between genotypes is unknown. We determined HCV genotype in 120 anti-HCV-positive patients with end-stage renal disease and on haemodialysis, by both serological assay (which showed evidence of previous exposure) and by two molecular assays: restriction fragment length polymorphism (RFLP) and line-probe reverse hybridization (LiPA). In mixing experiments, RFLP and LiPA was able to detect the minor HCV genotypes (if present) in 5-30% and 1-2% of the viral population, respectively. Of the 120 patients studied, genotype-specific antibodies were detected in 50 (42%), and eight patients had reactivities to peptides derived from multiple genotypes (genotypes 1 and 2 and/or 3). Only genotype 1 infection was found by RFLP/LiPA in these eight patients with reactivities to multiple HCV genotypes. One-hundred and five of the 120 (88%) patients were positive for HCV RNA by reverse transcription-polymerase chain reaction (RT-PCR) analysis and 14 were found to have mixed genotype infection. Follow-up serum samples (4-21 months later) were available in five patients (genotype 1a with another genotype/subtype). All five patients had a reduced number of HCV genotypes detected during follow-up; four of the five patients still had detectable genotype 1a, and one patient lost genotype 1a and was positive for genotype 2b only. These data showed that HCV mixed infection can be reliably detected by molecular methods and, in patients with end-stage renal disease and mixed genotype infection, there is a trend that during follow-up, HCV genotype 1 may prevail, or 'take over' the genotype 2 and 3 infection.

Hepatitis C virus genotype does not affect patient survival among renal transplant candidates. The New England Organ Bank Hepatitis C Study Group.

BACKGROUND: Patients with end-stage renal disease (ESRD) are at increased risk for infection with different hepatitis C virus (HCV) genotypes and multiple genotype infections. However, to date, the effect of the type and number of infecting HCV genotypes on survival among ESRD patients has not been carefully examined, and this was the objective of this study. METHODS: Sera from patients on the renal transplant waiting list at the New England Organ Bank between November 1986 and June 1990 were tested for anti-HCV using a third-generation enzyme-linked immunosorbent assay. All anti-HCV-positive serum samples were tested for HCV RNA by reverse transcriptase "nested" polymerase chain reaction (PCR) with primers derived from the highly conserved 5'UTR region of the HCV genome. HCV genotypes were determined by restriction fragment length polymorphism of the 5'UTR PCR product. The duration of follow-up was calculated from the date of the first available serum specimen until death, loss to follow-up, or December 31, 1995, whichever occurred earlier. Two separate multivariate models were constructed: one to examine the impact of HCV genotype on mortality and the other to examine the impact of the single versus mixed infection on mortality. In both models, the independent variables were HCV genotype and transplantation. The HCV genotype was treated as a time-independent (baseline) variable. Transplantation was treated as a time-dependent variable in which the status changed after transplantation. RESULTS: HCV RNA was detected by PCR in 224 patients (81%) in whom sera were available. Complete clinical data on baseline covariates, subsequent transplantation, and mortality were available in 180 patients (80%), and these patients constituted the final study cohort. HCV genotypes 1a and 1b were the two most common genotypes encountered and were found in 60 and 24% of the patients, respectively. One hundred and sixty-two (90%) patients were infected with a single HCV single genotype, 16 patients (9%) with two genotypes, and two patients (1%) with three genotypes. Among the 180 patients in the final study cohort, 86 (48%) underwent transplantation, and 66 (37%) patients died during follow-up. Compared with patients infected with HCV genotype 1a, the relative risk (RR) of death from all causes was not significantly increased among patients infected with genotype 1b (RR = 1.02, 95% CI, 0.55 to 1.89) or other genotypes (RR = 1.08, 95% CI, 0.50 to 2.30). Likewise, compared with patients with a single infection, the RR of death among patients with mixed infection (RR = 1.18, 95% CI, 0.52 to 2.66) was not significantly increased. CONCLUSIONS: The results of this study suggest that the type and number of HCV genotypes may not have a significant impact on survival among ESRD patients.

Interleukin-1 receptor antagonist synthesis by peripheral blood mononuclear cells in hemodialysis patients.

BACKGROUND: Pro-inflammatory cytokines like interleukin (IL)-1 beta and tumor necrosis factor-alpha (TANF-alpha) are believed to play a significant role in dialysis-related morbidity. It has been previously demonstrated that the endogenous synthesis of interleukin-1 receptor antagonist (IL-1Ra) is a reliable marker of the level of IL-1 beta synthesis in hemodialysis (HD) patients. In this study, we assessed the impact of clinical and laboratory variables on IL-1Ra synthesis by peripheral blood mononuclear cells (PBMC) in patients on HD with unsubstituted cellulose dialyzers. METHODS: IL-1Ra by PBMC was measured by a specific non-cross-reactive radioimmunoassay. Day to day variation in cytokine synthesis, the correlation between cytokine synthesis under different in vitro stimulatory conditions, and the influence of clinical and laboratory variables on cytokine synthesis were studied. RESULTS: Although there was a trend towards greater IL-1Ra synthesis by unstimulated, endotoxin-stimulated and IgG-stimulated PBMC drawn before the second and third dialysis sessions of the week when compared to the first dialysis treatment, this was not statistically significant. There was a strong correlation between IL-1Ra synthesis by PBMC cultured under different stimulatory conditions that was best observed between IL-1Ra cell content and from endotoxin-stimulated PBMC (r = 0.51, P = 0.0001), and endotoxin- and IgG-stimulated PBMC (r = 0.44, P = 0.0001). In addition, there was a close correlation between total synthesis (cell associated and secreted) and secreted levels of IL-1Ra in unstimulated (r = 0.59, P = 0.0001) and endotoxin-stimulated PBMC (r = 0.69, P = 0.0001). Interestingly, there was an inverse correlation between IL-1Ra synthesis and duration of dialysis that was strongest for secreted IL-1Ra from unstimulated (r = -0.50, P = 0.002) and endotoxin-stimulated PBMC (r = -0.34, P = 0.04). There was no significant correlation between IL-1Ra synthesis by PBMC and other clinical and laboratory indices. CONCLUSIONS: The observations from this study indicate that: (1) in HD patients, there were no significant differences in cytokine synthesis by PBMC drawn before the three different dialysis treatments during the week; (2) there is a close relationship between IL-1Ra synthesis from PBMC cultured under different stimulatory conditions; (3) the secreted levels of IL-1Ra correlate directly with total synthesis (cell-associated and secreted); (4) with the exception of duration of dialysis, none of the other clinical or laboratory parameters correlated with cytokine synthesis; and (5) the diminished endotoxin- or IgG-stimulated IL-1Ra synthesis with increasing time on dialysis is possibly another sign of the impaired host-defense system in patients on long-term hemodialysis.

Predictors of GBV-C infection among patients referred for renal transplantation.

The etiology of liver disease remains unknown in about 4 to 23% of dialysis patients and 10 to 16% of renal transplant recipients. A search for other causative agents of liver disease led to the discovery of the GB group of viruses. We studied the association between the presence of GB virus C (GBV-C) infection, known risk factors for parenterally-transmitted infections and history or laboratory evidence of liver disease among end-stage renal disease (ESRD) patients referred for renal transplantation to the New England Organ Bank, MA. Stored sera from patients on the renal transplantation waiting list between November 1986 and June 1990 were tested for antibody to hepatitis C virus (HCV). Sera were available in 1544 of 3243 (48%) patients, and anti-HCV was detected by ELISA3 in 287 (19%). All 287 anti-HCV positive patients formed the anti-HCV positive cohort and 286 randomly selected anti-HCV negative patients formed the anti-HCV negative cohort (573 patients overall). Additional sera were available for GBV-C RNA testing in 465 of 573 (81%) patients, and GBV-C RNA was detected by RT-PCR in 146. The overall extrapolated prevalence of serum GBV-C RNA was 29%. The prevalence of serum GBV-C RNa among anti-HCV positive patients (35%) was not significantly different from that among anti-HCV negative patients (29%; P = 0.22). In a univariate analysis, compared to patients without GBV-C RNA, patients with serum GBV-C RNA were younger [odds ratio (OR) 0.98 per year of age, P = 0.01], had a lower proportion of males (OR 0.64, P = 0.03), lower proportion of patients with diabetes mellitus (OR 0.44, P = 0.01), higher proportion of patients with a previous transplantation (OR 1.53, P = 0.04), longer duration of dialysis at the time of enrollment (OR 1.004 per month on dialysis, P = 0.03), and a higher proportion of patients with history of transfusions (OR 4.58, P = 0.01). Serum GBV-C RNA was not associated with a significantly increased OR for history of liver disease or non-A, non-B hepatitis, or elevated serum alanine aminotransferase levels. In a step-wise multivariate regression analysis, a younger age (OR 0.98 per year of age, P = 0.03), and history of blood transfusions (OR 3.89, P = 0.03) were associated with an increased OR for serum GBV-C RNA, while diabetes mellitus was associated with a decreased OR for GBV-C RNA (OR 0.47, P = 0.01). Anti-HCV was not a predictor of serum GBV-C RNA (OR 1.07, P = 0.77). The results of this study support the fact that GBV-C is a parenterally transmitted virus and shed light on the modes of transmission of GBV-C among ESRD patients. However, the association with liver disease remains to be established.

Serologic and virologic profiles of hepatitis C infection in renal transplant candidates. New England Organ Bank Hepatitis C Study Group.

The development of policies to prevent nosocomial transmission of hepatitis C virus (HCV) infection in hemodialysis units is critically dependent on the understanding of the relationship between tests for anti-HCV, HCV RNA, and HCV genotype and the patients' clinical characteristics. We tested sera from all patients on the renal transplant waiting list at the New England Organ Bank between November 1986 and June 1990 for anti-HCV by a third-generation enzyme-linked immunosorbent assay (ELISA3) and a third-generation recombinant immunoblot assay (RIBA3). All ELISA3-positive sera were tested for HCV RNA by reverse transcriptase "nested" polymerase chain reaction, and the genotype was characterized by restriction fragment length polymorphism. Sera were available in 1,544 of 3,243 (48%) patients on the waiting list, of whom 287 (19%) tested positive for anti-HCV by ELISA3. Two hundred eighty-six randomly selected, anti-HCV-negative patients served as controls. Compared with anti-HCV-negative controls, anti-HCV-positive patients had a longer duration since initiation of renal replacement therapy, higher number of previous kidney transplants and blood transfusions, higher proportion of patients with anti-HBc, history of liver disease, history of non-A, non-B hepatitis, and elevated serum alanine aminotransferase, and lower serum albumin concentrations. Of the 287 anti-HCV-positive sera, 261 (91%) were reactive by RIBA3, 21 (7%) were indeterminate, and five (2%) were nonreactive. HCV RNA was detected in 224 of 275 (81%) ELISA3-positive patients, in whom additional sera were available. There were no significant differences in clinical or laboratory characteristics between ELISA3-positive patients with and without HCV RNA. Genotypes 1a, 1b, 2a, 2b, 3a, and 4 were present in 53%, 23%, 8%, 10%, 4%, and 2% of patients, respectively. Infection with one, two, or three different HCV genotypes was present in 92%, 7%, and 1%, respectively. There was no significant association between the type or number of HCV genotypes and RIBA3 reactivity. There were no major differences in clinical or laboratory characteristics between genotypes or between single and mixed infection. In summary, this study provides detailed information regarding the relationship between tests for anti-HCV, HCV RNA, and HCV genotypes and the clinical and laboratory characteristics of a large, well-characterized cohort of patients referred for renal transplant.

Effects of hepatitis C infection and renal transplantation on survival in end-stage renal disease. The New England Organ Bank Hepatitis C Study Group.

Hepatitis C virus (HCV) infection is common among patients with end-stage renal disease (ESRD). However, the effect of HCV infection on survival among ESRD patients, and the impact of renal transplantation on the course of HCV infection has not been adequately defined. Sera from patients on the renal transplant waiting list at the New England Organ Bank between November 1986 and June 1990 were tested for anti-HCV using a third generation ELISA. All anti-HCV positive patients and a 1:1 ratio of randomly selected anti-HCV negative patients comprised the study sample. Duration of follow-up was calculated from the date of the first available serum specimen until death, loss to follow-up or December 31, 1995, whichever occurred earlier. Multivariate analysis of risk factors for mortality was performed using a Cox proportional hazards model which included anti-HCV as a time-independent (baseline) variable, transplantation as a time-dependent (follow-up) variable, and independently significant baseline covariates. Anti-HCV was detected in 287 (19%) of 1544 patients in whom sera were available, and 286 anti-HCV negative patients served as controls. Complete information was available in 496 (87%) of these 573 patients. Median follow-up was 73 months (range 1 to 110 months), during which time 302 (61%) patients underwent renal transplantation and 154 (31%) patients died. For anti-HCV positive patients compared to anti-HCV negative patients, the relative risk of death (and 95% confidence intervals) from all causes was 1.41 (1.01 to 1.97) and due to liver disease or infection was 2.39 (1.28 to 4.48). For patients who underwent transplantation compared to those who remained on dialysis, the relative risk of death from all causes between 0 to 3 months, 3 to 6 months, seven months to four years, and after four years was 4.75 (2.76 to 8.17), 1.76 (0.75 to 4.13), 0.31 (0.18 to 0.54) and 0.84 (0.51 to 1.37), respectively. There was no interaction between the effect of anti-HCV status as baseline and subsequent transplantation (P = 0.93), meaning that the association between treatment modality and survival was similar among anti-HCV positive and negative patients, at all intervals after transplantation. We conclude that HCV infection at the time of referral for transplantation is associated with an increased risk of death, irrespective of whether patients remain on dialysis or undergo transplantation. Transplantation has a beneficial rather than adverse effect on long-term survival in anti-HCV positive patients. Hence, anti-HCV positive status alone is not a contraindication for renal transplantation.

Hepatitis C in dialysis patients.

Patients on hemodialysis have a higher prevalence of hepatitis C (HCV) infection compared with the general population. Several factors have been associated with an increased risk of HCV infection in hemodialysis patients, including number of blood transfusions, duration of hemodialysis, previous transplantation, intravenous drug abuse, male gender, and in-center hemodialysis. In addition, there is mounting evidence to suggest nosocomial transmission within hemodialysis units. Although the precise modes of transmission have not been identified, breakdown in standard infection control practices, physical proximity to an infected patient, and sharing of dialysis machines are possible causes. Nonetheless, at the present time, the Centers for disease Control and Prevention (CDC) does not recommend dedicated machines, patient isolation, or a ban on re-use in hemodialysis patients with HCV infection. Consequently, strict adherence to universal precautions and careful attention to hygiene are recommended to reduce the transmission of HCV in dialysis units.

Impact of single use versus reuse of cellulose dialyzers on clinical parameters and indices of biocompatibility.

Hemodialysis with reprocessed dialyzers has been associated with an increased mortality in patients on chronic dialysis, but the causes for this increased mortality have not been identified thus far. The aim of this study was to compare the qualitative and/or quantitative differences in activation of cellular and plasma elements, intradialytic signs and symptoms, adequacy of dialysis, and serum biochemistry and hematology in patients dialyzed with new or reprocessed cellulose dialyzers. This study measured the plasma levels and production of interleukin-1 receptor antagonist (IL-1Ra) by peripheral blood mononuclear cells (PBMC), indices of cytokine synthesis; plasma C3a levels, an index of complement activation; plasma levels of lipopolysaccharide binding protein (LBP), an acute phase reactant; and plasma levels of bactericidal-permeability increasing factor (BPI), a neutrophil primary granule protein, in 37 patients on chronic hemodialysis with glutaraldehyde and bleach-reprocessed cellulose dialyzers after random assignment to 12 wk of dialysis with new (single use) or reprocessed (reuse) cellulose dialyzers. These indices were studied before dialysis, 15 min after the start of dialysis, and at the conclusion of dialysis in both groups. Intradialytic clinical symptoms and signs, urea reduction ratios, monthly blood chemistry, and hematology were also studied during the 12-wk period. Before randomization, clinical and laboratory characteristics and IL-1Ra production by PBMC were similar in the two groups. During the 12-wk study, the mean number of dialyzer reuses was 7 +/- 1 in the reuse group and there were no breaks in protocol in the single-use group. At the end of the study, plasma levels of IL-1Ra, cell content and production of IL-1Ra by unstimulated, endotoxin-stimulated, and lgG-stimulated PBMC among patients assigned to reuse were not significantly different from those in the single-use group either before dialysis, at 15 min, or at the conclusion of dialysis. Similarly, plasma levels of C3a, LBP, and BPl were not significantly different between groups at any of the three time points. During the 12-wk study, none of the patients in either arm of the study experienced chills, rigors, or fever, and there were no differences in the number of episodes of symptomatic hypotension in patients on reused dialyzers (11 +/- 3) compared with patients on single-use dialyzers (8 +/- 2). The mean monthly urea reduction ratio during the 3 months of the study was 63 +/- 2% and 65 +/- 2% for reuse and single-use dialyzers, respectively (not significant). Similarly, the hematocrit, white blood cell count, serum calcium, phosphorus, cholesterol, triglycerides, total protein, and albumin levels were also not significantly different between the two groups at the end of the 12-wk study period. These results suggest that the reprocessing of cellulose dialyzers with glutaraldehyde and bleach does not affect indices of blocompatibility, intradialytic symptoms and signs, adequacy of dialysis, or serum biochemistry and hematology.

Angiotensin converting enzyme inhibition and chronic cyclosporine-induced renal dysfunction in type 1 diabetes.

AIM: This study was designed to evaluate whether the angiotensin converting enzyme inhibitor enalapril could prevent cyclosporine-induced renal dysfunction in diabetic patients treated with CsA in monotherapy. DESIGN: Twenty-four recent onset insulin-dependent diabetic patients without prior renal involvement were randomized to receive a 3 month course of either cyclosporine (CsA) alone (7.5 mg/kg. b.i.d. in olive oil) or CsA+enalapril (20mg p.o. oad.). END POINTS: were mean arterial pressure, plasma creatinine, GFR, renal plasma flow, renal vascular resistance, sodium and lithium clearances measured before and after 3 months of treatment. RESULTS: Baseline values were identical in both groups except for mean arterial pressure which was slightly higher in the subjects subsequently receiving CsA + enalapril. Three month treatment with CsA increased significantly mean arterial pressure and renal vascular resistance by 9 and 24% respectively, while decreasing significantly glomerular filtration rate and renal plasma flow by 17 and 14% respectively. Enalapril was able to prevent the decline in GFR and the increase in blood pressure induced by CsA. This effect was demonstrated despite a similar increase in renal vascular resistance suggesting a dissociation between changes in glomerular filtration rate and renal vascular resistance during angiotensin converting-enzyme inhibition. CONCLUSION: Chronic angiotensin converting-enzyme inhibition could afford some degree of protection against CsA-induced renal dysfunction. Whether these results can be extrapolated to transplant recipients in whom CsA is usually associated to treatment by glucocorticosteroids deserves further evaluation.

Renal effects of angiotensin I-receptor blockade and angiotensin convertase inhibition in man.

1. The objective was to compare two means of inhibition of the renin-angiotensin system [angiotensin-converting enzyme inhibition and selective antagonism of angiotensin II subtype 1 (AT1) receptor] on renal function in 10 healthy normotensive volunteers on a normal sodium diet. Since mechanisms of action may differ between both drugs, a synergistic action was further studied by combining the two drugs. 2. The design was a double-blind randomized acute administration of either placebo or a single oral dose of enalapril, 20 mg, followed in each case by administration of the AT1 selective antagonist losartan potassium, 50 mg orally. 3. The methods included measurements of hormones (plasma renin activity, plasma aldosterone), blood pressure and renal function from 45 to 135 min after administration of placebo or enalapril, and from 45 to 135 min after losartan and placebo or losartan and enalapril. Renal function was studied using clearance of sodium, lithium, uric acid, inulin and para-aminohippuric acid. To examine further the determinants of glomerular filtration at the microcirculation level, fractional clearance of neutral dextran was determined and sieving curves were applied on a hydrodynamic model of ultrafiltration. 4. Losartan did not change plasma renin activity, blood pressure or glomerular filtration rate, but increased significantly renal plasma flow and urinary excretion of sodium and uric acid. Enalapril increased plasma renin activity and renal plasma flow, and decreased blood pressure without natriuretic, lithiuretic or uricosuric effects. The renal vasodilatation was potentiated when losartan and enalapril were combined, despite a further rise in plasma renin. In contrast to enalapril, losartan either alone or in combination with enalapril significantly depressed fractional clearances of dextran of small radii (34-42 A). These changes in fractional clearances of dextran were presumably related to the rise in glomerular plasma flow since the other major determinants of filtration, i.e. transcapillary glomerular pressure gradient, ultrafiltration coefficient and membrane property, were computed as unchanged by either losartan, enalapril or a combination of both. 5. In conclusion, these findings suggest that in normal sodium-repleted man the renal, hormonal and blood pressure effects of AT1 antagonism and angiotensin-converting enzyme inhibition are not strictly similar and could be synergistic.

Acute renal effects of neutral endopeptidase inhibition in humans.

The acute renal effects of neutral endopeptidase 24.11 (E-24.11) inhibition induced by a single oral dose of sinorphan (100 mg) were investigated in 10 healthy normotensive subjects on normal sodium diet. Sinorphan inhibited 90% of E-24.11 activity and increased plasma atrial natriuretic peptide (ANP) and urinary guanosine 3',5'-cyclic monophosphate (cGMP) by 70 and 100%, respectively. Sinorphan increased urinary sodium output by 50% (P < 0.001) and decreased fractional distal reabsorption by 4% (P < 0.01). Sinorphan increased glomerular filtration rate (GFR) and filtration fraction by 10% 1 h after administration and decreased renal plasma flow by 10%. Mean arterial pressure, renal vascular resistance, plasma aldosterone concentration, and renin activity were unmodified. Sinorphan decreased fractional clearance of neutral dextrans over the 34- to 52-A radius range. Applying the changes along with a hydrodynamic isopore with shunt model, sinorphan significantly increased capillary pressure gradient (delta P; 39 +/- 1 vs. 34 +/- 1 mmHg; P < 0.01), whereas ultrafiltration coefficient was unchanged. In conclusion, endopeptidase inhibition increased endogenous plasma ANP and cGMP generation and induced natriuresis through both an increase in filtered load and a decrease in distal tubular reabsorption of sodium. Sinorphan increases GFR, filtration fraction, and delta P, probably through an increase in efferent over afferent arteriolar resistance ratio.

Opposite renal effects of a PGE1 analog and prostacyclin in humans.

Renal effects of prostaglandins have been widely investigated in anesthetized animals, but in contrast only few studies have been devoted to healthy and diseased humans. Recently, both prostacyclin and a stable analog of PGE1, misoprostol, have been available for therapeutic purposes in clinical conditions associated with peripheral or renal vasoconstriction; however, the renal effects have not been defined. We have therefore studied the acute renal effects of PGI2 5 ng.kg/min intravenously and of misoprostol, a stable PGE1 analogue, 400 micrograms orally in two groups of respectively 8 and 12 healthy supine subjects on normal sodium diet using sodium, lithium, inulin, PAH and neutral dextran clearances. PGI2 induced a slight natriuretic effect, a systemic and renal vasodilation with a decrease in mean arterial pressure from 85.3 +/- 1.1 to 80.2 +/- 1.6 mm Hg (P < 0.01) and in renal vascular resistance from 94 +/- 6 to 75 +/- 5 mm Hg.min/ml (P < 0.001). GFR did not change whereas fractional clearance of dextran decreased over the 34 to 48 A radius range. Applying these changes on a hydrodynamic model of filtration of macromolecules through water-filled pores, we calculated that PGI2 decreased the glomerular transcapillary pressure gradient from 35 +/- 1 to 32 +/- 1 mm Hg (P < 0.001), decreased nonsignificantly the ultrafiltration coefficient Kf and did not affect the membrane parameters r0 and omega 0. Misoprostol had no natriuretic effect, induced slight renal vasoconstriction and moderate decrease in GFR from 124 +/- 9 to 114 +/- 10 ml/min.1.73 m2 (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Renal response to angiotensin after short-term angiotensin converting enzyme inhibition.

In 13 normotensive subjects on a normal sodium diet, we studied hormonal, blood pressure, and renal vascular changes and dextran sieving profiles induced by infusion of exogenous angiotensin II (Ang II) (5 ng.kg-1.min-1). during baseline conditions and after 5 days of administration of the angiotensin converting enzyme inhibitor cilazapril. Cilazapril induced a renal vasodilative effect without affecting supine blood pressure and glomerular filtration rate. Fractional dextran clearances were significantly decreased for dextran of effective radius ranging from 3.0 to 4.0 nm. This shift was primarily related to an increase in glomerular capillary plasma flow, because no change was observed in the transcapillary glomerular pressure gradient, the ultrafiltration coefficient, or the membrane parameters. Ang II elicited a slight pressor response accompanied by hormonal, antinatriuretic, and renal hemodynamic changes that were similar during and before short-term angiotensin converting enzyme inhibition. Dextran sieving curves were unchanged by a low dose of Ang II. However, the transcapillary glomerular pressure gradient and the ultrafiltration coefficient were computed to increase by 19.4% and to decrease by 44.2%, respectively, whereas membrane parameters were unaffected. When superimposed onto short-term angiotensin converting enzyme inhibition, glomerular response to this unique dose of Ang II was similar to that induced by Ang II alone. These findings indirectly suggest that most, if not all, of the renal effects of cilazapril are mediated through suppression of Ang II formation.

Renal abnormalities in normotensive insulin-dependent diabetic offspring of hypertensive parents.

To assess the effects of genetic predisposition of essential hypertension on early renal function in recent insulin-dependent diabetics, we studied inulin, para-aminohippuric, sodium, and lithium clearances in 69 unselected diabetics with (n = 20) and without (n = 49) a family history of essential hypertension. Despite similar metabolic control, glomerular filtration rate and mean arterial pressure were significantly higher in diabetics with than in those without a family history of hypertension. However, no difference was found between the two groups regarding renal vascular resistance, sodium excretion, or fractional proximal and distal sodium reabsorption. Renal responses to acute captopril (75 mg) administration were evaluated in 27 patients (six with family history of hypertension). Captopril decreased filtration fraction and mean arterial pressure similarly in both groups, whereas glomerular filtration rate and renal vascular resistance decreased more dramatically in diabetics with family history of hypertension. These findings indirectly suggest an abnormal response to angiotensin of vascular tone in recent diabetics with familial predisposition to hypertension. Renal response to acute nicardipine (2.5 mg i.v.) administration was analyzed in 24 patients (five with family history of hypertension). In both groups, nicardipine similarly decreased mean arterial pressure and renal vascular resistance and induced a marked natriuretic effect due to a predominant reduction in proximal reabsorption of sodium. However, the increase in sodium excretion was twofold to threefold more pronounced in diabetics with a family history of hypertension. Whether these early renal abnormalities may contribute to the risk of diabetic nephropathy, as suggested by retrospective studies, remains to be determined.