Changes in the morphology of ribosomes in uterine epithelial cells under various hormonal conditions.

The ultrastructural morphology of "free" cytoplasmic ribosomes of rat uterine epithelial cells was studied during diestrus, estrus, after ovariectomy, and after estradiol-17 beta administration to rats that were ovariectomized 1 to 25 weeks before hormone treatment. A change in size and contrast of ribosomes was observed concomitant with a transition from pre-existing monosomes to polysomes depending on the dose of estradiol and its route of application. In 3 weeks ovariectomized rats these changes in ribosomal granules take place at approximately the same time (30-45 min) when synthesis of "induced protein" was described biochemically. The morphological events after estradiol administration are discussed with respect to a primary site of estrogen action.