Induction of Type II 5′-Deiodinase Activity in Cultured Rat Astroglial Cells by 12-O-Tetradecanoylphorbol-13- Acetate: Dependence on Glucocorticoids

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Abstract
The effect of an activator of protein kinase C, 12-0-tetradecanoylphorbol-13-acetate (TPA), on the 5′-deiodinase (5′D) activity was studied in rat astroglial cells cultured in chemically defined medium. TPA promoted a large increase in the type II 5′D activity, which was maximal 5-10 h after addition of TPA and then declined to the basal level at 24 h. The optimal TPA concentration was 10−7 M. TPA and 8-Br-cAMP, an other inducer of 5′D activity were antagonist. Otherwise, TPA stimulated 5′D activity only in the presence of glucocorticoids at concentrations from 10−8 M to 10−4 M. Glucocorticoids alone induced a slight increase in 5′D activity. These data indicate that protein kinase C contributes to the control of 5′D activity in astroglial cells and that its action is dependent on glucocorticoids.