Physicochemical Characterization of Photoaffinity-Labeled Angiotensin II Receptors

TLDR: Specific receptor sites for angiotensin II (AII) were analyzed in the adrenal cortex and other target tissues including liver, anterior pituitary gland, and smooth muscle, after covalent labeling with the radioactive photoaffinity analog 125I-[Sar1,(4-N3)Phe8]-AII.

Abstract: Specific receptor sites for angiotensin II (All) were analyzed in the adrenal cortex and other target tissues including liver, anterior pituitary gland, and smooth muscle, after covalent labeling with the radioactive photoaffinity analog 125l-[Sar1,(4-N3)Phe8]-All. The photoreactive All derivative retained high affinity for adrenal receptors and full steroidogenic activity in adrenal glomerulosa cells. In bovine adrenal cortex, covalent labeling of All receptors by the photoreactive analog was specifically inhibited by [Sar1]All with an IC50 of about 5 nm. The Mr of the covalent All-receptor complex during polyacrylamide gel electrophoresis of the labeled protein under reducing conditions was 58,000. Under nonreducing conditions, a minor band with Mr of 105,000 was also observed. Two labeled species were also found during gel permeation chromatography of the detergent-solubilized complex, with Mrs of 64,000 and 86,000. The pl of the solubilized photolabeled complex was absorbed to wheat germ lectin Sephar...