Renal functional response to captopril during diuretic therapy.

Antihypertensive agents may modify the renal effects of angiotensin converting enzyme inhibition (ACEI). This potential interaction, which is important in the diagnosis of renovascular hypertension was studied in two rat models with and without diuretic treatment prior to ACEI. Acute intravenous administration of furosemide or hydrochlorothiazide in one-kidney, one-clamp animals (1K1C) did not change glomerular filtration rate (GFR) or effective renal plasma flow (ERPF). ACEI administration after furosemide and hydrochlorothiazide decreased GFR (p less than 0.001, p less than 0.01) but not ERPF. Chlorothiazide administered to 1K1C prior to ACEI, decreased GFR (p less than 0.02) but not ERPF captopril administration to 1K1C which received hydrochlorothiazide intraperitoneally for 7-10 days decreased GFR (p less than 0.007) and ERPF (p less than 0.02), while two-kidney, one-clamp animals (2K1C) decreased GFR only in the clamped kidney (p less than 0.005). ERPF in 2K1C increased only in the contralateral kidney (p less than 0.01). Without diuretic 1K1C animals decreased GFR and ERPF after ACEI (p less than 0.005, P less than 0.001). In the clamped kidney of 2K1C rats, GFR and ERPF decreased significantly (p less than 0.0005, p less than 0.004) and contralateral kidney ERPF increased (p less than 0.001), but GFR did not. The consequences of ACEI on GFR are similar with or without diuretic. These data suggest that diuretic therapy may not significantly interfere with ACEI evaluation of renovascular hypertension.