Evidence that Rat Pineal Thyroxine 5′-Deiodinase is Primarily Stimulated by β - and not α -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 > 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 β-adrenergic agonists and requiring new RNA and protein synthesis for its activation.