HORMONAL REGULATION OF INTESTINAL lip-HYDROXYSTEROID DEHYDROGENASE J. P&ha’, I. MikSik, V. Lisa and I. Pohlova

We have previously demonstrated the developmental increase of the activity of 11 P-hydroxysteroid dehydrogenase (11 PHSD) 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 1lPHSD 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 (lo-’ M), dexamethasone ( 10m7 M), triiodothyronine (low7 M) or insulin (lo-’ M) and 11 PHSD activity was evaluated by measuring the conversion of [3H]corticosterone to [3H]1 1-dehydrocorticosterone. The activity of 1lPHSD 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 1 IPHSD activity.