The effect of angiotensin II antagonist, Sar1-Ile8-angiotensin II, on furosemide-induced increase in plasma noradrenaline, renin activity and aldosterone in unanesthetized dogs.

Abstract

In order to evaluate the role of the renin-angiotensin system and the sympathetic nervous system in the maintenance of blood pressure in the sodium-depleted state, the changes of plasma renin activity (PRA), plasma aldosterone concentration (PAC) and plasma noradrenaline (PNA) were examined in unanesthetized dogs after the administration of furosemide. Furthermore, the role of the renin-angiotensin system in the increased sympathetic nerve activity induced by furosemide was assessed by using Sar1-Ile8-angiotensin II, an angiotensin II antagonist. When a dose of 0.8 mg/kg of furosemide was injected intravenously, 3 times every 15 minutes, PRA and PNA were significantly increased with a concomitant increase in PAC. Sar1-Ile8-angiotensin II induced a significant increase in PAC and a slight increase in PRA, while no changes were found in PNA and the mean blood pressure. The increase in PNA induced by furosemide was inhibited dose-dependently by Sar1-Ile8-angiotensin II, through PRA and PAC were further increased. There results suggest that an administration of furosemide induced the increase in PNA and the increase in PNA by furosemide might by mediated by the renin-angiotensin system.