Steroids as potential modulators of angiotensin receptors in bovine adrenal glomerulosa and kidney

Abstract

To test the hypothesis that there is feedback inhibition of adrenal angiotensin receptors by substances released in response to the peptides, we measured binding of labeled angiotensins in the presence of various steroids. Approximately half of the 70 steroids tested inhibited binding of labeled angiotensin II and III to intact and broken cells from bovine adrenal glomerulosa and kidney, but the concentrations required for inhibition were relatively high. The most potent inhibitors were 3α, 5β tetrahydroaldosterone and tetrahydrodeoxycorticosterone (ID 50 = 8 × 10 −5 M). Kinetic analysis showed that inhibition was mostly competitive. Among steroids whose reduced congeners were tested, potency increased in the sequence: parent steroid < 5α dihydroderivative < 5β dihydro derivative < 3α, 5β tetrahydro-derivative. Tetrahydrodeoxycorticosterone inhibited aldosteronogenesis by intact cells at concentrations that inhibited angiotensin binding. Steroids differentially inhibited binding of labeled angiotensin II and III, and discriminated between receptors in adrenal glomerulosa and kidney. The results provide additional evidence for heterogeneity of angiotensin receptors, and lead to the prediction that any normal or pathological inhibition of angiotensin receptors by steroids will be mediated by reduced derivatives.