The research goals for the coming year include a number of studies utilizing the newly developed radioimmunoassay procedure to measure plasma vasopressin which is presently being used routinely in our laboratory. Studies will continue which are directed toward obtaining quantitative information regarding the role of the vasopressin system in both the short-term and long-term control of arterial blood pressure. The open-loop feedback gain of the vasopressin system will be determined over a broad range of arterial pressures. The role of the low-pressure atrial stretch receptors and the high-pressure baroreceptors in the control of vasopressin release will be investigated. The influence of circulating angiotensin and by studying the effects of the converting enzyme inhibitor. SQ-14,225 on vasopressin secretion in a salt depleted state. Additionally, base-line data is being obtained to characterize the influence of excess sodium, and sodium depletion on vasopressin secretion in dogs and man. Finally, long-term infusions intravenous and intrarenal, of prostaglandin E2, F2 alpha and I2 are being systematically pursued to determine the influence of these substances on long-term renal function and upon the control of arterial blood pressure.