Biphasic Stimulation of Aldosterone Secretion during Hemorrhage in Dogs

The increase of aldosterone secretion in response to hemorrhage has been reevaluated with the aid of a newly developed micromethod using gas-liquid chromatography. Pentobarbital-anesthetized large male dogs were slowly exsanguinated through the lumboadrenal vein while sequential 15-minute samples of adrenal venous effluent were collected. Mean arterial blood pressure and blood loss were monitored. The response to hemorrhage was found to be biphasic; a significant increase in aldosterone secretion occurred before blood pressure changed significantly, the secretory rates then fell toward control, and rose again as the blood pressure fell to shock levels. Statistical evaluation of the data confirmed the quartic nature of the response and indicated a best-fit equation of y = 169.14x − 800.22x + 1258.46x − 619.24x.These results demonstrate that control of aldosterone secretion is dependent on complex functions of blood volume and blood pressure. Volume receptor mechanisms as well as pressure receptor mechanisms would seem to be involved. Any investigation of the aldosterone response to hemorrhage, to be valid, must take these complex relationships into consideration.