Angiotensin II Receptors in Bovine Adrenal Cortex

AngiotensinII binding to adrenal cortex receptors is inhibited with high specificity by GTP, 5'-guanilylimidophosphate, (Gpp(NH)p), and ITP.Half-maximum inhibition of angiotensin II binding is achieved with 1.6 X 1O-7 M GTP in the presence of a nucleotide-regenerating system, and Gpp-(NH)p is equally effective in the absence of the nucleotideregenerating system.Guanosine 3': 5'-monophosphate, 5'-GMP, ATP, and UTP demonstrate little or no inhibition at concentrations which were l,OOO-to lO,OOO-fold higher than those of Gpp(NH)p or GTP.Inclusion of the guanyl nucleotides (GTP and Gpp(NH)p) in the binding assay leads to a lower steady state binding of the hormone to its receptor, and addition of these nucleotides to the binding assay at steady state leads to a rapid release of bound tracer angiotensin II.It is proposed that these actions of the guanyl nucleotides are based on a conformational change at the receptor level.