The aim of proposed studies is to evaluate the factor or factors responsible for regulation of the number and affinity of angiotensin II receptors of several target tissues. These studies will involve simultaneous evaluations in both adrenal and vascular tissues of the rat. In addition, I aim to provide a physiologic explanation for a possible role for angiotensin receptors in several well described states of altered responsiveness to angiotensin II. The effect of potassium, nephrectomy, and angiotensin infusions will be compared. The angiotensin II radioreceptor assay of rat adrenal and smooth muscle will be used to quantify any alterations in the number or affinity of angiotensin receptors in target tissues. The aldosterone responses to angiotensin II (both in vivo and in vitro) and pressor responses to angiotensin II will be evaluated following the same physiologic maneuvers. All of the proposed studies will be done in the rat.