Induction of Type II 5′-Deiodinase Activity by Cyclic Adenosine 3′, 5′-Monophosphate in Cultured Rat Astroglial Cells

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Abstract
Cultured astroglial cells were found to contain a type II 5′-deiodinase (5′D) activity which was increased by 10-3 M (Bu)2cAMP but not by 2 x 10-3 M n-butyrate. 8-Bromo-cAMP (8-Br-cAMP) (10-3 M) also increased this enzyme activity. Cycloheximide (2 μg/ml) inhibited the 8-Br-cAMP effect on 5′D activity. Forskolin (10-8 M), cholera toxin (5 μg/ml), 10-5 M isoproterenol, and 3 × 10-6 M norephinephrine also increased the 5′D activity of astroglial cells. After a 4-h incubation these agents or cAMP analogs had maximal effect, and enzyme activities were 6- to 14-fold above control value. The stimulatory effects of isoproterenol and norepinephrine were almost completely reversed after 8 h incubation. The induction of 5′D activity by isoproterenol or norepinephrine was inhibited by the β-adrenergic antagonist alprenolol (5 × 10-6 M). The effect of norepinephrine was not significantly affected by the α1-adrenergic antagonist, prazosin (10-5M). Thus, 5′D activity is controlled by agents increasing cAMP in astroglial cells, and in particular by the neurotransmitter, norephinephrine, via β-adrenergic mechanism. (Endocrinology123: 1577–1581, 1988)