Effect of enalapril and losartan on the events that precede diabetic nephropathy in rats

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Abstract
Background Mesangial cell proliferation, phenotype change, and increased transforming growth factor‐β (TGF‐β) precede mesangial expansion in diabetic rats. Experiments using mesangial cell culture have shown that angiotensin II increases TGF‐β production by these cells. The aim of the present study was to investigate the effect of enalapril and losartan on the events that precede diabetic nephropathy in rats. It was also analyzed if the determination of urinary TGF‐β could be a mean for the evaluation of therapeutic efficacy in this disease. Methods Eighty‐two female Wistar rats were made diabetic by intravenous injection of streptozotocin diluted in citrate buffer, and citrate buffer alone was injected into the control group (N = 34). Ten days later, the right kidney was removed. Thirty diabetic rats were treated with enalapril, DMN + E, in drinking water (20 mg/L) and 24 with losartan, DMN + L (50 mg/L). Urinary TGF‐β was determined 90 days after STZ or buffer injection, the animals were killed, and the kidneys were removed for histological and immunohistochemical studies. Results The immunostaining for TGF‐β and fibronectin in the cortical tubulointerstitium and glomeruli was higher in untreated diabetic rats (p < 0.001). Treatment with enalapril or losartan reduced this increase. The urinary TGF‐β excretion (pg/mg urinary creatinine) was 48.6 ± 5.9 in control animals, 603.9 ± 80.41 in untreated diabetic rats, 279.3 ± 47.0 in diabetic rats treated with enalapril, and 243.7 ± 40.0 in rats treated with losartan. Conclusions We concluded that enalapril or losartan treatment can modify events that precede diabetic nephropathy by reducing TGF‐β and fibronectin expression in glomeruli and tubulointerstitium as well as urinary TGF‐β content. Copyright © 2002 John Wiley & Sons, Ltd.

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