Effect of angiotensin II antagonism on the regression of kidney disease in the rat.

BACKGROUND: Normalization of proteinuria and even regression of glomerulosclerosis seem to occur in progressive renal disease upon blockade of the renin-angiotensin system. Here we quantified the effect of a combination of an angiotensin converting enzyme (ACE) inhibitor and an angiotensin II (Ang II) receptor antagonist on renal function and structure in spontaneous overt nephropathy in male Munich Wistar Fromter (MWF) rats. METHODS: Three groups of MWF rats were used: group 1 was studied at 25 weeks to provide baseline renal function and structure; group 2 was followed until 40 weeks of age; group 3 was treated with lisinopril (40 mg/L) and valsartan (180 mg/L) in drinking water from 25 to 40 weeks. A group of untreated Wistar rats (group 4, 40 weeks) was used as the control. At the end of the study renal hemodynamics, kidney tissue morphology, accumulation of type III collagen and evaluation of interstitial inflammatory cells were performed. RESULTS: MWF rats spontaneously developed hypertension, proteinuria, glomerulosclerosis, interstitial volume expansion and protein cast accumulation. Combined treatment completely reversed protein excretion and ameliorated renal plasma flow and the glomerular ultrafiltration coefficient. The combined therapy was effective in halting progressive glomerulosclerosis, particularly in glomeruli with mild sclerotic lesions, and reduced interstitial volume expansion. Type III collagen accumulation and protein cast also were reversed. Infiltrating cells were massively present in the interstitium already at 25 weeks, and augmented at 40 weeks in untreated rats. Combined treatment reduced infiltrating cells to values comparable to normal controls. CONCLUSIONS: These data indicate that in animals with spontaneous overt nephropathy, Ang II antagonism normalized proteinuria, eliminated inflammatory cell infiltration, and ameliorated glomerular and tubular structural changes.

Effect of high dose ramipril with or without indomethacin on glomerular selectivity.

BACKGROUND: Despite the accumulating evidence of their efficacy, angiotensin-converting enzyme inhibitors (ACEi) still provide imperfect renoprotection. Up-titration above conventional doses and combined therapy with other antiproteinuric agents may serve to achieve renoprotection in patients at risk of rapid disease progression. METHODS: The effect of maximum tolerated ACEi doses (ramipril 15 mg/day, range 5 to 20) alone or combined with indomethacin (75 mg x 2/day) on urinary protein excretion (UPE) and glomerular barrier size-selective function was evaluated in 19 patients with chronic non-diabetic nephropathies and persistent proteinuria. RESULTS: Maximum ramipril doses decreased UPE more effectively than non-ACEi therapy. Proteinuria reduction was associated with significant reduction (>50%) of the non-selective glomerular membrane shunt, but did not correlate with concomitant changes in arterial pressure and renal hemodynamics, nor was it influenced by treatment duration. The reduction in UPE and sieving coefficient of the largest neutral dextrans exceeded by twofold the reduction achieved by conventional ACEi doses in historical controls with similar renal dysfunction and proteinuria, previously studied under identical experimental conditions. Indomethacin did not influence renal effects of maximum ramipril doses and was prematurely withdrawn in six patients because of reversible side effects. Serum potassium significantly increased only in combination with indomethacin and never required treatment withdrawal. CONCLUSIONS: Up-titration to maximally tolerated doses safely increases ACEi antiproteinuric effect and may serve to achieve maximum renoprotection in the long-term. Combination with indomethacin is poorly tolerated and ineffective. Innovative approaches are needed to use ACEi more effectively.