Evidence that Rat Pineal Thyroxine 5'-Deiodinase is Primarily Stimulated by - and not -Adrenergic Agonists and that Its Adrenergic-Stimulated and Spontaneous Rhythmic Nocturnal Rise Require RNA and Protein Synthesis

Abstract

Pineal thyroxine 5'-deiodinase (5'-D) activity rose greater than 10-fold above the basal level 2-3 hr after 1 mg/kg isoproterenol and returned to near the basal level by 6 hr. The same dose of norepinephrine or phenylephrine was without effect, but phenylephrine modestly potentiated isoproterenol-stimulated 5'-D activity. Either actinomycin D or cycloheximide treatment markedly decreased diurnal isoproterenol stimulation and the spontaneous rhythmic nocturnal rise of pineal 5'-D. The data indicate that pineal 5'-D activity is very similar to pineal serotonin N-acetyl transferase in being primarily stimulated by beta-adrenergic agonists and requiring new RNA and protein synthesis for its activation.