Role of the Renin-Angiotensin System in the Vasopressin Response to Hemorrhage

The dependence of vasopressin release in response to hemorrhage on the reninangiotensin system was investigated. A nonhypotensive hemorrhage of 12 ml/kg body weight (approximately 15% of the blood volume) was used as a stimulus for vasopressin release in anesthetized dogs. The right renal artery and vein were ligated, and a snare was placed around the left renal blood vessels. When the renal artery and vein were unobstructed by the snare, hemorrhage resulted in an increase in both the plasma vasopressin concentration and the plasma renin activity. When the renal vessels were occluded, hemorrhage resulted in a greater increase in the plasma vasopressin concentration, although the plasma renin activity remained unchanged. It would appear that the renin-angiotensin system does not play an important role in stimulating vasopressin release in response to a reduction in blood volume in the anesthetized dog. (Endocrinology90: 453, 1972)