We have previously demonstrated the developmental increase of the activity of 11beta-hydroxysteroid dehydrogenase (11betaHSD) in the rat ileum which correlated with the developmental surge of plasma concentrations of corticosteroids, thyroid hormones and insulin. To ascertain whether these hormones directly stimulate 11betaHSD activity we used explant cultures of ileum and distal colon. The intestinal segments of young, 7-day-old rats, were cultured 48 hours in the presence of aldosterone (10[-7] M), dexamethasone (10[-7] M), triiodothyronine (10[-7] M) or insulin (10[-7] M) and 11betaHSD activity was evaluated by measuring the conversion of [3H]corticosterone to [3H]11-dehydrocorticosterone. The activity of 11betaHSD was significantly increased following 48 h treatment with dexamethasone and aldosterone, whereas insulin and triiodothyronine were without any effect. Corticosterone oxidation was inhibited by carbenoxolone and progesterone. It is being concluded, that both glucocorticoids and mineralocorticoids but not insulin or triiodothyronine induce intestinal 11betaHSD activity.

Institute of Physiology Czech Academy of Sciences Prague Czech Republic

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