5/6 nephrectomy as a validated rat model mimicking human warfarin-related nephropathy.

BACKGROUND/AIMS: We previously reported that patients with chronic kidney disease (CKD) receiving warfarin therapy and whose international normalized ratio increases to >3.0 may develop acute kidney injury (AKI) as a result of glomerular hemorrhage and formation of obstructive red blood cell (RBC) casts. We named this condition warfarin-related nephropathy (WRN). We also previously reported that acute excessive anticoagulation with brodifacoum (superwarfarin) induces AKI in 5/6 nephrectomy (5/6NE) rats. Limitations of the brodifacoum model precluded a careful assessment of dose-response relationships. METHODS: Warfarin treatment was used in 5/6NE. RESULTS: Herein we report that warfarin treatment of 5/6NE rats resulted in a dose-dependent increase in serum creatinine (SC). The increase in SC following warfarin treatment was greater at 3 and 19 weeks after the ablative surgery, than that observed 8 weeks after the ablative surgery. The SC increase was correlated with the prothrombin time increase. Morphologically, 5/6NE, but not control rats, had acute tubular injury with RBC and RBC casts in the tubules. Treatment with vitamin K prevented SC increase and morphologic changes in the kidney associated with warfarin treatment. A single episode of WRN did not affect the progression of CKD in 5/6NE. CONCLUSION: (1) The 5/6NE model of CKD is an appropriate animal model to study the pathogenesis of WRN. (2) The pharmacokinetics of warfarin is better suited to the study of WRN than that of brodifacoum. (3) The more advanced stages of 5/6NE are more susceptible to WRN than the earlier stages. (4) Vitamin K treatment prevents WRN.

Evidence that abnormally large seasonal declines in vitamin D status may trigger SLE flare in non-African Americans.

Cross-sectional studies have shown that low vitamin D (25-hydroxyvitamin D (25(OH)D)) is associated with increased systemic lupus erythematosus (SLE) activity. This study is the first to assess the temporal relationship between 25(OH)D levels and onset of SLE flare. This assessment was made possible because of the specimen bank and database of the Ohio SLE Study (OSS), a longitudinal study of frequently relapsing SLE that involved regular bimonthly patient follow-up. We identified for this study 82 flares from 46 patients that were separated by at least 8 months from previous flares. Serum 25(OH)D levels were measured at 4 and 2 months before flare, and at the time of flare (a flare interval). We found that for flares occurring during low daylight months (LDM, Oct-Mar), 25(OH)D levels were decreased at the time of flare, but only in non-African American (non-AA) patients (32% decrease at flare, compared to 4 months prior, p < 0.001). To control for seasonal effects, we also measured 25(OH)D levels in the LDM "no-flare" intervals, which were intervals that matched to the same calendar months of the patients' LDM flare intervals, but that didn't end in flare (n = 24). For these matches, a significant decrease occurred in 25(OH)D levels during the flare intervals (18.1% decrease, p < 0.001), but not during the matching no-flare intervals (6.2% decrease, p = 0.411). For flares occurring during high daylight months (HDM), 25(OH)D levels changed only in non-AA patients, increasing slightly (5.6%, p = 0.010). Analysis of flare rates for the entire OSS cohort (n = 201 flares) revealed a tendency for higher flare rates during LDM compared to HDM, but again only in non-AA patients (p = 0.060). Flare rates were lower during HDM for non-AA patients compared to AA patients (p = 0.028). In conclusion, in non-AA SLE patients, unusually large declines in 25(OH)D during LDM may be mechanistically related to SLE flare, whereas relatively high 25(OH)D levels during HDM may protect against flare.

Vitamin D deficiency as marker for disease activity and damage in systemic lupus erythematosus: a comparison with anti-dsDNA and anti-C1q.

OBJECTIVES: To study the sensitivity and specificity of vitamin D deficiency for predicting disease activity and damage of systemic lupus erythematosus (SLE) in comparison with anti-dsDNA and anti-C1q. METHODS: Consecutive patients who fulfilled four or more ACR criteria for SLE were studied. Levels of 25-hydroxyvitamin D3, anti-C1q, anti-dsDNA and complement levels were measured. Relationship among these markers, concurrent disease activity and damage scores of SLE was studied by Spearman's rank correlation method. RESULTS: In total, 290 SLE patients were studied (95% women; mean age 38.9 ± 13.1 years; SLE duration 7.7 ± 6.7 years). Clinical or serological lupus activity (SLEDAI ≥ 1) was present in 225 (78%) patients. Vitamin D deficiency (< 15 ng/ml) was detected in 78 (27%) patients. Levels of 25-hydroxyvitamin D3 correlated inversely with the clinical SLE disease activity score (Rho = -0.26; p < 0.001). A negative correlation was also observed between 25-hydroxyvitamin D3 and anti-dsDNA levels (Rho = -0.13; p = 0.02), or anti-C1q (Rho = -0.14; p = 0.02). However, there was no significant relationship between levels of 25-hydroxyvitamin D3 and complement C3 (Rho = 0.09; p = 0.12) or C4 (Rho = 0.09; p = 0.13). Both 25-hydroxyvitamin D3 deficiency and anti-C1q were more specific but less sensitive than anti-dsDNA for concurrent clinical renal and non-renal SLE activity. Levels of 25-hydroxyvitamin D3, anti-dsDNA or anti-C1q did not correlate significantly with the SLE damage scores. CONCLUSIONS: 25-hydroxyvitamin D3 correlated inversely and significantly with clinical SLE activity, anti-C1q and anti-dsDNA titers, but not with complement levels or damage scores. Deficiency of 25-hydroxyvitamin D3 was as specific as anti-C1q, but less sensitive than anti-dsDNA, for detecting concurrent renal and non-renal clinical activity of SLE.

The complex nature of serum C3 and C4 as biomarkers of lupus renal flare.

To assess the relationship between serum C3 or C4 levels and lupus renal flare, C3 and C4 levels were measured bimonthly in 71 lupus nephritis patients for a mean of 35 months, during which time 70 renal flares were identified. Comparing baseline, pre-flare, and at-flare values indicated that neither C3 nor C4 levels decreased pre-flare, but both decreased on average significantly at flare. However, sensitivity/specificity for C3 (75%/71%) and C4 (48%/71%) were low. To account for other influencing factors, multiple regression was performed that included bimonthly values of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), and genotype data on C3 (S/F), CRP (1846G > A), and the complement regulator factor H (Y402H). This analysis revealed that reduced levels of C4, but not C3, were independently associated with the two-month pre-flare period. Conversely, reduced levels of C3, but not C4, were independently associated with the flare visit. Significant pro-flare interactions included low C3 levels with the factor H 402HH-encoding genotype, and low CRP levels with the C3 F allele. Together these data suggest that C4 activation is critical for initiating renal flare while C3 activation is involved in the actual tissue damage, and that these effects are influenced by genetic variability in complement activation and regulation.

Phenotypes, genotypes and disease susceptibility associated with gene copy number variations: complement C4 CNVs in European American healthy subjects and those with systemic lupus erythematosus.

A new paradigm in human genetics is high frequencies of inter-individual variations in copy numbers of specific genomic DNA segments. Such common copy number variation (CNV) loci often contain genes engaged in host-environment interaction including those involved in immune effector functions. DNA sequences within a CNV locus often share a high degree of identity but beneficial or deleterious polymorphic variants are present among different individuals. Thus, common gene CNVs can contribute, both qualitatively and quantitatively, to a spectrum of phenotypic variants. In this review we describe the phenotypic and genotypic diversities of complement C4 created by copy number variations of RCCX modules (RP-C4-CYP21-TNX) and size dichotomy of C4 genes. A direct outcome of C4 CNV is the generation of two classes of polymorphic proteins, C4A and C4B, with differential chemical reactivities towards peptide or carbohydrate antigens, and a range of C4 plasma protein concentrations (from 15 to 70 mg/dl) among healthy subjects. Deliberate molecular genetic studies enabled development of definitive techniques to determine exact patterns of RCCX modular variations, copy numbers of long and short C4A and C4B genes by Southern blot analyses or by real-time quantitative PCR. It is found that in healthy European Americans, the total C4 gene copy number per diploid genome ranges from 2 to 6: 60.8% of people with four copies of C4 genes, 27.2% with less than four copies, and 12% with more than four copies. Such a distribution is skewed towards the low copy number side in patients with systemic lupus erythematosus (SLE), a prototypic autoimmune disease with complex etiology. In SLE, the frequency of individuals with less than four copies of C4 is significantly increased (42.2%), while the frequency of those with more than four copies is decreased (6%). This decrease in total C4 gene copy number in SLE is due to increases in homozygous and heterozygous deficiencies of C4A but not C4B. Therefore, it is concluded that lower copy number of C4 is a risk factor for and higher gene copy number of C4 is a protective factor against SLE disease susceptibility.

Thiazide diuretic monotherapy for hypertension: diuretic's dark side just got darker.

Diuretic monotherapy is the current recommendation of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure for initial antihypertensive therapy. There is mounting concern, however, that the benefits of diuretic's superior blood pressure control may be offset by its multiple metabolic disturbances that increase cardiovascular risk. Reungjui et al. document a new concern, nephrotoxicity by thiazide monotherapy. This and other recently published evidence of diuretic's 'dark side' is discussed.

Spot urine protein/creatinine ratios are unreliable estimates of 24 h proteinuria in most systemic lupus erythematosus nephritis flares.

The diagnosis of glomerulonephritis flares in systemic lupus erythematosus (SLE) is usually based on whether the magnitude of proteinuria has changed. Our study tests two methods to assess proteinuric change: protein/creatinine (P/C) ratios of intended 24-h urine collections or that of spot urine samples. Sixty-four patients with glomerulonephritis due to SLE followed in the Ohio SLE Study provided bimonthly paired spot and intended 24-h urine collections. Completeness of each collection was estimated as the ratio of the measured creatinine to the expected creatinine based upon Cockroft-Gault. Intended 24-h urine collections with measured/expected creatinine ratios between 0.5 and 0.9 (237 samples overall) showed ratios that were not significantly different from ratios of complete 24-h urine collections with ratios of 0.9-1.1 (159 samples). To compare spot and 24 h P/C ratios, we randomly selected pairs of samples with measured/expected ratios above 0.75. Consistent with previous studies, spot and 24-h urine P/C ratios showed good correlation over the range of values as well as reasonably strong concordance. Over the range of most SLE glomerulonephritis flares, however, correlation was present but concordance was poor. Our work suggests that the use of spot urine P/C ratios will yield more false-positive and -negative diagnoses of glomerulonephritis flares in patients with SLE than the ratio in 24-h urines.

Consumption of erythrocyte CR1 (CD35) is associated with protection against systemic lupus erythematosus renal flare.

Erythrocyte complement receptor type one (E-CR1) is thought to protect against immune complex (IC) disease through interactions that lead to E-CR1 consumption, and low E-CR1 levels are characteristic of systemic lupus erythematosus (SLE). The purpose of this study was to test the hypothesis that E-CR1 consumption can predict or mark SLE flare. Recurrently active SLE patients [n = 43; 28 with past or present major renal manifestations (SLER) and 15 without (SLENR)], were evaluated every 2 months by detailed protocol testing (mean follow-up 22 months), including direct measurements of E-CR1 levels using a radioimmunoassay. In all patients, detectable E-CR1 levels fluctuated widely through acute periods of consumption and regeneration, preventing the use of any single value as a baseline. However, when individual chronic baseline values were used, determined as the mean of all E-CR1 values 4 months or more from a flare, a clear trend was observed. In 16 of 16 instances of non-renal flare in SLER patients, E-CR1 levels decreased at flare (mean decrease 34%, P < 0.0001). In contrast, no consistent difference was observed for flare in SLENR patients or for renal flare in SLER patients. Changes in E-CR1 levels did not correlate with plasma CR1 levels. In conclusion, single occurrences of E-CR1 consumption did not generally predict or mark SLE flare. However, compared to the average E-CR1 levels measured during no-flare intervals, E-CR1 consumption in SLER patients at flare was strongly associated with freedom from signs of renal involvement. We postulate that E-CR1 consumption reflects E-CR1 function that includes protecting against SLE nephritis.

Of mice and men: the relevance of the mouse to the study of human SLE.

A number of mouse models have been utilized to study the pathophysiology of immune complex (IC) disease, and the hallmark IC disease systemic lupus erythematosus (SLE). Many of these studies have provided exciting new insights into IC-mediated inflammation and autoimmunity. However, numerous differences exist between mice and humans that suggest that mouse studies are not always applicable to human disease. These differences can be found in the biological systems that interact with circulating IC, in the specifics of disease presentation, and in the general physiology of the two species. Furthermore, although the mechanisms of SLE-like autoimmune disease in the mouse are being defined through analyses of the murine models of SLE, it remains to be proven that these mechanisms are relevant to human SLE. Thus, generalizing the results of the mouse studies to human SLE and other human IC diseases must be done with caution.

The urgent call of albuminuria/proteinuria. Heeding its significance in early detection of kidney disease.

Microalbuminuria, one of the earliest indicators of kidney injury, could be a harbinger of progressive kidney failure. Similarly, it can also be one of the early signs that a patient at risk for cardiovascular disease is in fact developing the disease. If so, the patient's therapy is failing. Discussion of specific appropriate interventions are beyond the scope of this article. However, publications referred to in this work have recently discussed such interventions in substantial practical detail. Ample evidence shows that factors that are kidney-protective are also cardiovascular-protective.

CR1 and CR1-like: the primate immune adherence receptors.

Immune adherence describes the phenomenon in which complement-opsonized substrates, such as immune complexes (IC), viruses, or bacteria, are bound by primate erythrocytes via erythrocyte complement receptors. In vivo studies have shown that this binding allows the erythrocyte to act as an inert shuttle, targeting IC to the monocyte phagocytic system and away from vulnerable tissue. Thus, immune adherence appears to play an integral role in the primate in promoting the safe clearance of circulating IC and preventing IC-mediated pathologies. The complement receptors that mediate immune adherence comprise two unique but closely related gene products, either the type one complement receptor (CRI) in humans or CRI-like in non-human primates. This review focuses on the structure, function, and physiological role of the primate immune adherence receptors.

Renoprotection: one or many therapies?

BACKGROUND: Renal disease that progresses to end-stage renal disease (ESRD) imposes a great burden on the affected individual and on society, which mainly bears the cost of ESRD (currently more than $10 billion to treat about 333,000 patients annually in the U.S.). Thus, there is a great need to identify therapies that arrest the progression mechanisms common to all forms of renal disease. Progress is being made. Perhaps the most visible advance is the randomized controlled trials (RCT) demonstrating the renoprotective effects of angiotensin-converting enzyme (ACE) inhibitors. There are also numerous other promising renoprotective therapies. Unfortunately, testing each therapy in RCT is not feasible. Thus the nephrologist has two choices: restrict renoprotective therapy to those shown to be effective in RCT, or expand the use of renoprotective therapies to include those that, although unproven, are plausibly effective and prudent to use. The goal of this work is to provide the documentation needed for the nephrologist to choose between these strategies. METHODS: This work first describes the mechanisms believed to be involved in the progression of renal disease. Based largely on this information, 18 separate interventions that slow the progression are described. Each intervention is assigned a level of recommendation (Level 1 is the highest and Level 3 the lowest) according to the strength of evidence supporting its renoprotective efficacy. RESULTS: The number of interventions at each level of recommendation are: Level 1, N = 4; Level 2, N = 4; Level 3, N = 10. Our own experience with the multiple-risk-factor intervention is that most patients can achieve the majority of the Level 1 and 2 interventions, and many of the Level 3 interventions. We recommend the expanded renoprotection strategy. CONCLUSION: This work advances the hypothesis that, until better information becomes available, a broad-based, multiple-risk-factor intervention intended to slow the progression of renal disease can be justified in those with progressive nephropathies. This work is intended primarily for clinical nephrologists and thus each recommended intervention is described in substantial practical detail.

Cyclosporine in patients with steroid-resistant membranous nephropathy: a randomized trial.

BACKGROUND: A clinical trial of cyclosporine in patients with steroid-resistant membranous nephropathy (MGN) was conducted. Although MGN remains the most common cause of adult-onset nephrotic syndrome, its management is still controversial. Cyclosporine has been shown to be effective in cases of progressive MGN, but it has not been used in controlled studies at an early stage of the disease. METHODS: We conducted a randomized trial in 51 biopsy-proven idiopathic MGN patients with nephrotic-range proteinuria comparing 26 weeks of cyclosporine treatment plus low-dose prednisone to placebo plus prednisone. All patients were followed for an average of 78 weeks, and the short- and long-term effects on renal function were assessed. RESULTS: Seventy-five percent of the treatment group versus 22% of the control group (P < 0.001) had a partial or complete remission of their proteinuria by 26 weeks. Relapse occurred in 43% (N = 9) of the cyclosporine remission group and 40% (N = 2) of the placebo group by week 52. The fraction of the total population in remission then remained almost unchanged and significant different between the groups until the end of the study (cyclosporine 39%, placebo 13%, P = 0.007). Renal function was unchanged and equal in the two groups over the test medication period. In the subsequent follow-up, renal insufficiency, defined as doubling of baseline creatinine, was seen in two patients in each group, but remained equal and stable in all of the other patients. CONCLUSION: This study suggests that cyclosporine is an effective therapeutic agent in the treatment of steroid-resistant cases of MGN. Although a high relapse does occur, 39% of the treated patients remained in remission and were subnephrotic for at least one-year post-treatment, with no adverse effect on filtration function.

Proximal tubular epithelial hyperplasia in patients with chronic glomerular proteinuria.

BACKGROUND: Proteinuria is known to affect the proximal tubular epithelial structure and function. The present study tested the hypothesis that chronic proteinuria leads to hyperplasia of proximal tubular epithelium. METHODS: This hypothesis was tested by morphometric analysis of the renal biopsy specimens in two groups of patients. Group A (N = 15) was composed of patients with chronic glomerular proteinuria who, for clinical indications, underwent renal biopsy of their native kidneys on two separate occasions. The proteinuria was sustained during the first and second renal biopsies in all but two of the patients with minimal change nephrotic syndrome who experienced transient remission. Group B (N = 10) was composed of patients with little or no proteinuria who underwent renal biopsy because of unexplained hematuria and whose renal biopsy showed only thin glomerular basement membrane (GBM) disease. RESULTS: In Group A, the mean number of epithelial cell nuclei per proximal tubule cross-section increased significantly from the first to the second renal biopsy (11.0 +/- 2.7 vs. 13.0 +/- 2.2, P = 0.005, paired t-test). Also, those with severe proteinuria showed proximal tubules with reactive epithelium (large pale nuclei with a high nucleus to cytoplasm ratio) and marked hyperplasia (double and triple layers of epithelium). Such changes were not seen in group B renal biopsies. Compared with group A biopsies, group B biopsies showed a lower mean value for proximal tubular epithelial cell nuclei per tubular cross-section (P = 0.056) and a higher mean proximal tubular volume (P = 0.049). As a consequence, the mean number of nuclei per relative tubular volume was significantly greater in group A compared with group B (0.55 +/- 0.14 vs. 0.40 +/- 0.06, P = 0.003, by Wilcoxon rank sum). CONCLUSIONS: Chronic heavy proteinuria is associated with hyperplasia of proximal tubular epithelium and contraction of proximal tubular volume. These events may impair glomerular filtration and represent another mechanism of progression of renal disease.

A randomized trial of cyclosporine in patients with steroid-resistant focal segmental glomerulosclerosis. North America Nephrotic Syndrome Study Group.

UNLABELLED: A randomized trial of cyclosporine in patients with steroid-resistant focal segmental glomerulosclerosis. BACKGROUND: A clinical trial of cyclosporine in patients with steroid-resistant focal segmental glomerulosclerosis (FSGS) was conducted. Despite the fact that it is the most common primary glomerulonephritis to progress to renal failure, treatment trials have been very limited. METHODS: We conducted a randomized controlled trial in 49 cases of steroid-resistant FSGS comparing 26 weeks of cyclosporine treatment plus low-dose prednisone to placebo plus prednisone. All patients were followed for an average of 200 weeks, and the short- and long-term effects on renal function were assessed. RESULTS: Seventy percent of the treatment group versus 4% of the placebo group (P < 0. 001) had a partial or complete remission of their proteinuria by 26 weeks. Relapse occurred in 40% of the remitters by 52 weeks and 60% by week 78, but the remainder stayed in remission to the end of the observation period. Renal function was better preserved in the cyclosporine group. There was a decrease of 50% in baseline creatinine clearance in 25% of the treated group compared with 52% of controls (P < 0.05). This was a reduction in risk of 70% (95% CI, 9 to 93) independent of other baseline demographic and laboratory variables. CONCLUSIONS: These results suggest that cyclosporine is an effective therapeutic agent in the treatment of steroid-resistant cases of FSGS. Although a high relapse rate does occur, a long-term decrease in proteinuria and preservation of filtration function were observed in a significant proportion of treated patients.

Remission of nephrotic syndrome in type 1 diabetes: long-term follow-up of patients in the Captopril Study.

In 1994, we reported a 3.4 +/- 0.8 year follow-up of the eight patients who experienced remission of nephrotic syndrome during the Collaborative Study Group-sponsored, multicenter trial of captopril therapy in patients with type 1 diabetes with nephropathy (Captopril Study). Of the 409 patients randomized to treatment on the Captopril Study, 108 had nephrotic syndrome (24-hour proteinuria >/= 3.5 g of protein) at baseline. Of these 108 patients, 8 experienced remission of nephrotic syndrome (proteinuria

Effects of immune complex formation and complement activation on circulating platelets in the primate.

Primate platelets are different from rodent and rabbit platelets in that they do not express receptors for C3a or C5a or immune adherence receptors. This study assessed the effects of immune complex (IC)-induced complement activation on primate platelets in the circulation. Cynomolgus monkeys (CYN, N = 4) immunized to bovine gamma globulin (BGG) were infused with BGG over 5 min to induce acute intravascular IC formation and complement activation. The studies were carried out under normal complement conditions (N = 12), partial complement inhibition (CAB-2 treated, N = 3), or total complement inhibition (CVF treated, N = 1). Under normal complement conditions, BGG infusion increased C3a levels from undetectable to an average of 11.9 +/- 2.6 micrograms/ml. At this time, decreases occurring in both circulating neutrophils (85 +/- 6%) and monocytes (78 +/- 6%) were significantly greater than decreases in circulating platelets (13 +/- 3%, p < 0.001). Partial complement inhibition had an equivocal effect on the BGG-induced changes in circulating leukocytes, while total complement inhibition abrogated these changes. In contrast, platelet changes were unaffected by complement inhibition. We conclude that, compared to circulating leukocytes, circulating platelets are insensitive to intravascular complement activation induced by IC in the nonhuman primate. These results contrast with previous studies in rodents which demonstrate strong effects of IC-induced intravascular complement activation on both circulating neutrophils and platelets.

Mycophenolate mofetil therapy in lupus nephritis: clinical observations.

Controlled clinical trials in renal transplantation have demonstrated that mycophenolate mofetil is well tolerated and has lower renal transplant rejection rates than azathioprine regimens. This study reports on the clinical experiences at two institutions with mycophenolate mofetil (MMF) for severe lupus nephritis. Twelve patients with relapsing or resistant nephritis previously treated with cyclophosphamide therapy and one patient who refused cyclophosphamide as initial therapy for diffuse proliferative nephritis but accepted MMF were included. During combined MMF/prednisone therapy, serum creatinine values remained normal or declined from elevated values: mean change in serum creatinine was -0.26+/-0.46 microM/L, P = 0.039. Proteinuria significantly decreased: mean change in urine protein-to-creatinine ratios was -2.53+/-3.76, P = 0.039. Decreased serum complement component C3 and elevated anti-double-stranded DNA antibody levels at baseline improved in some, but not all, patients. The mean initial dose of MMF was 0.92 g/d (range, 0.5 to 2 g/d). The mean duration of therapy was 12.9 mo (range, 3 to 24 mo). Adverse events included herpes simplex stomatitis associated with severe leukopenia (n = 1), asymptomatic leukopenia (n = 2), nausea/ diarrhea (n = 2), thinning of scalp hair (n = 1), pancreatitis (n = 1), and pneumonia without leukopenia (n = 1). Recurrence of the pancreatitis led to discontinuation of MMF in this patient; all other adverse events resolved with dose reduction. It is concluded that MMF is well tolerated and has possible efficacy in controlling major renal manifestations of systemic lupus erythematosus. Controlled clinical trials are needed to define the role of MMF in the management of lupus nephritis.

Combination ACE inhibitor and angiotensin II receptor antagonist therapy in diabetic nephropathy.

The benefit of angiotensin-converting enzyme (ACE) inhibitor (i) therapy in diabetic glomerulosclerosis is thought to be largely the result of attenuation of angiotensin II (AngII) effects on blood pressure, glomerular hemodynamics and hypertrophy, and tissue fibrosis. The present study was undertaken to determine whether the addition of AngII receptor antagonist therapy to ACEi therapy in diabetic nephropathy results in attenuation of AngII effects beyond that achieved by ACEi therapy alone. Seven patients were studied as inpatients on the General Clinical Research Center each for 3 consecutive weeks as follows: week 1, the patients' usual regimen which included daily oral moderate to high dose ACEi therapy; week 2, the patients' usual regimen plus oral losartan (an antagonist (a) of the angiotensin type 1 receptor, AT1) 50 mg (n = 3) or 100 mg (n = 4) daily; week 3, return to the patients' usual regimen. Diet, physical activity, and blood glucose were held as constant as possible during the three weeks of daily testing. We found that plasma renin levels increased significantly during combination therapy and then returned to baseline values with discontinuation of AT1a therapy: mean baseline renin values (week 1) 3.0 ng/ml/min +/- 1.1 SE, mean renin values during combination therapy (week 2) 7.0 ng/ml/min +/- 3.2 (p = 0.0078 by Wilcoxon rank sum test), mean renin values after discontinuation of AT1a therapy (week 3) 3.9 ng/ml/min +/- 2.0 (NS compared to baseline values). In addition, 2 patients developed transient hypotension when losartan therapy was initiated. During this short-term study, 24-hour proteinuria, serum creatinine, serum potassium, and plasma aldosterone were not changed significantly by combination therapy. We conclude that in patients with diabetic nephropathy addition of AT1a therapy to ACEi therapy attenuates AngII effects better than ACEi therapy alone. We suggest that combination therapy for the management of diabetic glomerulosclerosis merits further investigation.