Effect of Actinomycin D on Hormones That Control the Release of Thyrotropin from the Anterior Pituitary Glands of Mice

Abstract

TRF and T3 have been shown previously to act on the anterior pituitary gland (APG), T3 inhibiting the releasing activity of TRF in a quantitative fashion. This study shows that actinomycin D can prevent or impair the inhibiting effect of T3 on release of TSH by TRF. Actinomycin D inhibited this T3 effect even when the antibiotic was administered 6 hr before the injection of T3. When actinomycin D was administered 1 hr after the injection of T3, it essentially had no effect on this T3 action. The effect of actinomycin D on the T3 block probably does not occur by decreasing the uptake of T3 into the APG. When actinomycin D was given to mice in amounts and at time intervals known to decrease the T3 block, it was found that the total RNA synthesis was decreased by 50% in APG but protein synthesis was not impaired. As reported previously for puromycin and cycloheximide, actinomycin D does not affect the TRF-TSH release response. (Endocrinology82: 303, 1968)