Inhibition of Adenylate Cyclase in Rat Adrenal Glomerulosa Cells by Angiotensin II*

Adenylate cyclase in homogenates of rat adrenal glomerulosa cells was inhibited in a concentration dependent manner by angiotensin II (AII). The maximum inhibition of basal activity was 34.5 +/- 2.7% and the EC50 value for AII was 1.1 +/- 0.4 nM (n = 6). Similar maximum inhibitions were produced by the precursor decapeptide, AI, and the heptapeptide, AIII [(des asp) AII]. The EC50 values for these two peptides were respectively 72 +/- 8 nM and 25 +/- 5 nM (n = 6). The antagonist compound (1-sarcosine, 8-isoleucine)-AII, reversed the effect of AII. Inhibition of the adrenal enzyme required guanosine triphosphate and monovalent cations as has been described for adenylate cyclase inhibition in other tissues. Maximum inhibition was observed at 10(-5) M guanosine triphosphate and 150 mM Na+ or Li+ ion. Both basal adenylate cyclase activity and activity stimulated by adrenocorticotrophic hormone were inhibited. These results demonstrate the presence in rat adrenal glomerulosa cells of angiotensin receptors coupled to adenylate cyclase inhibition and show that their properties are similar to those of adrenal angiotensin receptors described previously.