Captopril avoids hypertension, the increase in plasma angiotensin II but increases angiotensin 1–7 and angiotensin II-induced perfusion pressure in isolated kidney in SHR

1. We investigated captopril effects, an ACE inhibitor, on hypertension development, on Ang II and Ang-(1-7) plasma concentrations, on Ang II-induced contraction in isolated kidneys, and on kidney AT1R from spontaneously hypertensive (SHR) rats.
2. Five weeks-old SHR and Wistar Kyoto (WKY) rats were treated with captopril at 30 mg/kg/day, in drinking water for 2 or 14 weeks. Systolic blood pressure (SBP) was measured, and isolated kidneys were tested for perfusion pressure and AT1R expression; while Ang II and Ang-(1-7) concentrations were determined in plasma.
3. Captopril did not modify SBP in WKY rats and avoided its increase as SHR aged. Plasma Ang-II concentration was ∼4-5 folds higher in SHR rats, and captopril reduced it (P < 0.05); while captopril increased Ang-(1-7) by ∼2 fold in all rat groups.
4. Captopril increased Ang II-induced pressor response in kidneys of WKY and SHR rats, phenomenon not observed in kidneys stimulated with phenylephrine, a α₁-adrenoceptor agonist.
5. Captopril did not modify AT1R in kidney cortex and medulla among rat strains and ages.
6. Data indicate that captopril increased Ang II-induced kidney perfusion pressure but not AT₁R density in kidney of WKY and SHR rats, due to blockade of angiotensin II synthesis; however, ACE inhibitors may have other actions like activating signaling processes that could contribute to their diverse effects.