The role of angiotensin(1–7) in renal vasculature of the rat

OBJECTIVE: Angiotensin(1-7) is an active component of the renin-angiotensin-aldosterone system. Its exact role in renal vascular function is unclear. We therefore studied the effects of angiotensin(1-7) on the renal vasculature in vitro and in vivo. METHODS: Isolated small renal arteries were studied in an arteriograph system by constructing concentration-response curves to angiotensin II, without and with angiotensin(1-7). In isolated perfused kidneys, the response of angiotensin II on renal vascular resistance was measured without and with angiotensin(1-7). The influence of angiotensin(1-7) on angiotensin II-induced glomerular afferent and efferent constriction was assessed with intravital microscopy in vivo under anaesthesia. In freely moving rats, we studied the effect of angiotensin(1-7) on angiotensin II-induced reduction of renal blood flow with an electromagnetic flow probe. RESULTS: Angiotensin(1-7) alone had no effect on the renal vasculature in any of the experiments. In vitro, angiotensin(1-7) antagonized angiotensin-II-induced constriction of isolated renal arteries (9.71 +/- 1.21 and 3.20 +/- 0.57%, for control and angiotensin(1-7) pre-treated arteries, respectively; P < 0.0005). In isolated perfused kidneys, angiotensin(1-7) reduced the angiotensin II response (100 +/- 16.6 versus 72.6 +/- 15.6%, P < 0.05) and shifted the angiotensin II dose-response curve rightward (pEC50, 6.69 +/- 0.19 and 6.26 +/- 0.12 for control and angiotensin(1-7) pre-treated kidneys, respectively; P < 0.05). Angiotensin(1-7), however, was devoid of effects on angiotensin-II-induced constriction of glomerular afferent and efferent arterioles and on angiotensin-II-induced renal blood flow reduction in freely moving rats in vivo. CONCLUSION: Angiotensin(1-7) antagonizes angiotensin II in renal vessels in vitro, but does not appear to have a major function in normal physiological regulation of renal vascular function in vivo.