Renal microvascular actions of angiotensin II fragments

2001.—In the present study, we investigated renal micro-vascular responses to ANG-(1–7) and ANG IV. Diameter changes of small interlobular arteries, afferent arterioles, and efferent arterioles were assessed by using isolated per-fused hydronephrotic rat kidneys. ANG-(1–7) and ANG IV concentration dependently decreased the diameters of all investigated renal microvessel, however, with a much lower potency than ANG II. The ANG II type 1 receptor blocker irbesartan completely reversed the responses to ANG-(1–7) and ANG IV, whereas the ANG II type 2 receptor blocker PD-123319 had no effect. Both ANG-(1–7) and ANG IV failed to alter renal microvascular constriction induced by ANG II. In addition, subnanomolar concentrations of ANG-(1–7) had no effect on the myogenic-induced tone of interlobular arter-ies and afferent arterioles. Thus our data indicate that at high concentrations, ANG-(1–7) and ANG IV are able to activate the ANG II type 1 receptor, thereby inducing renal microvascular constriction. The failure of ANG-(1–7) and ANG IV to reduce ANG II- and pressure-induced constric-tions suggests that these fragments do not exert a vasodilator and/or ANG II antagonistic action in the kidney. angiotensin-(1–7); angiotensin IV; renal microvasculature; isolated perfused hydronephrotic rat kidney DURING THE LAST DECADE, EVIDENCE has accumulated that in addition to ANG II, ANG II fragments such as th