Control by progesterone of the concentration of lipid droplets in epithelial cells of the sheep endometrium.

T HE concentration of lipid droplets was determined histochemically in the epithelial cells of the sheep uterus during the estrous cycle and after ovariectomy and hormone treatment. Lipid droplet concentrations were lowest on days 4 to 6 of the cycle and increased to a maximum by day i0. They remained at a high level until after estrus, when they gradually declined to their lowest Ievel on days 4 to 6. Lipid droplets appeared in the epithelial cells as the corpus luteum developed, and the injection of progesterone into ovariectomized ewes increased the lipid content of epithelial ceils to a level comparable to that of luteal phase cycling ewes. Progesterone appears to control the formation of lipid droplets. The administration of estradiol to ewes immediately following ovariectomy on day 5 decreased the concentration of lipid droplets (P< .01) .