ESTROGEN-INDUCED FORMATION OF UTERINE RIBOSOMES

Abstract

Ribosomes with a sedimentation coefficient of 78S are in greater abundance in the cytoplasm of estrogen-stimulated uterine cells than in those deprived of hormone. From 4 to 24 hr. following estrogenic stimulation, newly formed ribosomes appear in the cytoplasm, and this represents a means whereby steroid hormones can regulate the protein-synthesizing apparatus of the cells. Studies of uridine-H3 labeling of ribosomes following estrogenic stimulation indicate clearly that the rate of ribosome formation has been linearly accelerated in comparison to controls. This may be of interest to those concerned with the kinetics of ribosome formation. The estrogenic acceleration of rate of uterine ribosome formation is an actinomycin D-and puromycin-sensitive process. These findings are interpreted as representing a secondary response of the uterus to the DNA-dependent, primary action of estrogen, which may be gene activation or derepression.