Solubilized adrenal angiotensin II receptors: studies on the site of action of sodium and calcium ions, and on the role of disulfide bridges.

The zwitterionic detergent, 3[(3-cholamidopropyl)dimethylammonio)-1-propane sulfonate (CHAPS), was used to extract angiotensin receptors from the adrenal zona glomerulosa of two species, the rat and beef. The solubilized receptors retained the different properties displayed by particulate receptors in these two species, as well as a preserved affinity and specificity. Moreover, the adrenal receptors lost their ability to be affected by sodium and calcium ions, and by guanyl nucleotides, indicating that the site of action of these modulators is distinct from the receptor itself. Dithiothreitol treatment enhanced the binding of agonist ([125I]angiotensin II) and antagonist (125I-angiotensin II) to particulate and solubilized rat adrenal receptors, an effect attributable to inhibition of tracer degradation. In contrast, agonist and antagonist binding to particulate bovine receptors was decreased by dithiothreitol, but agonist binding to soluble receptors was increased. In addition to showing important species differences in angiotensin-degrading activity of adrenal receptor preparations, this work suggests that bovine receptors may contain essential sulfhydryl groups for binding and recognition of angiotensin peptides as agonists or antagonists.