Renal injury in obese Zucker rats: glomerular hemodynamic alterations and effects of enalapril

Angiotensin-converting enzyme inhibitors may ameliorate experimental glomerular injury by either hemodynamic or nonhemodynamic mechanisms. In a long-term study, we examined the effects of 30 wk of enalapril treatment on the development of glomerular disease in obese Zucker rats (OZR). Enalapril significantly (P less than 0.05) lowered blood pressure, fasting serum cholesterol, and urine albumin excretion in OZR throughout the experimental period. At 38 wk of age, enalapril-treated OZR had a sixfold reduction in the percent glomeruli exhibiting focal glomerulosclerosis and a 20-30% reduction in kidney weight and glomerular area. A separate micropuncture study in 22- to 26-wk-old rats revealed that untreated OZR with albuminuria and increased blood pressure had elevated glomerular capillary pressure (Pgc). Enalapril-treated OZR had less albuminuria and lower blood pressure, but Pgc was not reduced. The value of the transcapillary hydraulic pressure difference (delta P) in enalapril-treated OZR was intermediate between values in untreated OZR and lean Zucker rats. Thus enalapril markedly attenuated the development of glomerular injury in OZR. The salutary effects of enalapril may have involved a reduction in delta P coupled to a nonhemodynamic action, possibly restriction of glomerular growth or lowering of serum cholesterol.