Post-nephrectomy changes in adrenal angiotensin II receptors in the rat; influence of exogenous angiotensin and a competitive inhibitor

Abstract

3H-angiotensin binding sites have been studied in a particulate fraction prepared from rat adrenal glands. This binding is rapid and reversible, of high affinity (KD29 degrees C = 3-5 X 10(-9) M) and with demonstrable specificity for the angiotensin II octapeptide. The number of binding sites varies with endogenous angiotensin levels: nephrectomy is followed by an increase in number of binding sites. This increase can be prevented by chronic angiotensin II administration and, to a lesser extent, by administration of Sar1,Ala8-angiotensin II, a competitive antagonist of the hormone. No variation in the equilibrium dissociation constant accompanied these changes in binding capacity. The post-nephrectomy increase in capacity is time-dependent, with a lag period of 24-40 h. The observed changes in receptor concentration do not appear explicable on the basis of receptor occupancy. Accordingly, angiotensin II receptors in the rat adrenal appear to be dependent on circulating angiotensin levels as previously reported for rat uterus.