Effects of enalapril on endothelin-1 and growth factor gene expression in diabetic rat glomeruli

We have previously reported that the mRNA levels of endothelin (ET-1), tumor necrosis factor-alpha), (TNF-alpha), platelet-derived growth factor (PDGF)-B chain, transforming growth factor (TGF-beta), and basic fibroblast growth factor (bFGF) all increased with age in diabetic rat glomeruli. We have now assessed the effect of the angiotensin-converting enzyme inhibitor enalapril on the expression of the ET-1, TNF-alpha, PDGF-B, TGF-beta, and bFGF genes in 24-week-old rat glomeruli after streptozotocin injection. Animals were divided into controls, enalapril-treated diabetic rats, and untreated diabetic rats. Treatment continued for 24 weeks. Enalapril reduced both creatinine clearance (p < 0.001) and urinary protein excretion (p < 0.01) in diabetic rats. Enalapril produced a nonsignificant 15 mm Hg reduction in blood pressure in diabetic rats. Enalapril also attenuated the increases in ET-1 mRNA levels observed in the glomeruli of diabetic rats (0.5-fold compared with untreated diabetic rats at 24 weeks [p < 0.01]) but had no effect on increased mRNA levels of TNF-alpha, PDGF-B, TGF-beta, and bFGF. These findings suggest that enalapril therapy may be effective in reducing ET-1 mRNA expression in the glomeruli of diabetic nephropathy.