MECHANISM OF ACTION OF SPIRONOLACTONE ON CORTISOL PRODUCTION BY GUINEA-PIG ADRENOCORTICAL-CELLS

[摘要] Studies were done to determine the mechanism(s) of action of spironolactone (SL) and of its deacetylated metabolite, 7-alpha-thio-SL, to inhibit cortisol secretion by guinea pig adrenocortical cells in vitro. Preincubation of cells at 37-degrees-C with SL or with 7-alpha-thio-SL caused a time-dependent decline in subsequent ACTH-stimulated cortisol secretion. In the absence of a preincubation, neither compound affected cortisol production, indicating the need for production of an active metabolite. When the 17-alpha-hydroxylase inhibitor, SU-10'603, was included during the preincubation period, neither SL nor 7-alpha-thio-SL decreased cortisol secretion, indicating the involvement of the 17-alpha-hydroxylase in the activation of both compounds. By contrast, neither the 11-beta-hydroxylase inhibitor, metyrapone, nor the cholesterol sidechain cleavage inhibitor, aminoglutethimide, diminished the effects of SL or of 7-alpha-thio-SL on cortisol secretion. Preincubation of cells with SL or 7-alpha-thio-SL also decreased the conversion of exogenous progesterone to cortisol, but did not affect cortisol production from the 17-alpha-hydroxylated substrates, 17-alpha-hydroxyprogesterone and 11-deoxycortisol, suggesting that only 17-alpha-hydroxylation was impaired. In addition, there was a decline in 17-alpha-hydroxylase activity in microsomes isolated from cells preincubated with SL or with 7-alpha-thio-SL, but no change in microsomal 21-hydroxylase or in mitochondrial 11-beta-hydroxylase and cholesterol sidechain cleavage activities. The results indicate that the direct effects of SL and of 7-alpha-thio-SL on the adrenal cortex to decrease cortisol production result from the selective inhibition of 17-alpha-hydroxylation. Since 17-alpha-hydroxylase activity is apparently required for the activation of both compounds, suicide inhibition of the enzyme may be the mechanism of action.

[发布日期] 1991-10-01

[关键词] SPIRONOLACTONE;CORTISOL PRODUCTION;ADRENOCORTICAL CELL;(GUINEA PIG)