Role of Angiotensin II in Hemorrhagic Hypotension in the Rat

Abstract

The purpose of this study was to evaluate the role of the renin-angiotensin system in the acute regulation of blood pressure following hemorrhage in the anesthetized rat. Eleven Sprague-Dawley rats were anesthetized with sodium pentobarbital. After control blood pressure recordings from the femoral artery were made, the rats were hemorrhaged 6 ml/kg body weight. Forty minutes after hemorrhage, the Angiotensin II antagonist, l-SAR-8-ALA-Angiotensin II (saralasin), was infused (10 /Ltg/min/kg) for 35 min. Hemorrhage resulted in a 53% decrease in blood pressure which recovered to 82% of the control blood pressure in 40 minutes. Infusion of saralasin resulted in a 24% decrease (p <0.01) in blood pressure within 15 min. Recovery from saralasin infusion occurred within 10 min as blood pressure increased back to control values. A second group of 5 rats was not hemorrhaged but was infused with saralasin. There were no significant changes in blood pressure; although, a tendency to decrease was noted reflecting the increase in plasma renin activity which occurs with anesthesia. It was concluded that the renin-angiotensin system can respond rapidly to a hypotensive event and aid in the restoration of blood pressure within minutes.