, Volume 35, Issue 6, pp 625-629

In vivo and in vitro studies of the site of inhibitory action of omeprazole on adrenocortical steroidogenesis

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The site of omeprazole inhibition of adrenal steroidogenesis has been sought in vivo by analyzing the patterns of urinary steroid metabolite excretion after 6 days of treatment with placebo/omeprazole.

Excretion rates of androsterone, aetiocholanolone, dehydroepiandrosterone, 11 β hydroxyandrosterone, tetrahydrocortisone, tetrahydrocortisol and α cortolone were reduced, indicating a block at an early step in steroidogenesis, possibly cholesterol side-chain cleavage. In vitro studies have confirmed this finding by measuring conversion of added precursors to cortisol in isolated bovine adrenocortical cells. Cortisol synthesis from added 20 α hydroxycholesterol was inhibited by 83% in the presence of 100 µg omeprazole/ml. Conversion from pregnenolone and progesterone and their 17 α hydroxylated derivatives was inhibited by 20–40% whereas cortisol production from added 11 deoxycortisol was not affected.

These data suggest that omeprazole primarily inhibits cholesterol cleavage and does not inhibit 3 β hydroxysteroid dehydrogenase, 17 α hydroxylase or 11 β hydroxylation; 21 hydroxylase activity may be marginally attenuated.