Glucocorticoids stimulate the accumulation of lipids in the rat corpus luteum

We investigated the physiological basis for the trophic effect of glucocort icoids in rat corpora lutea in the absence of pituitary gonadotropins. Imma ture (Day 29) Sprague-Dawley rats were given eCG and hCG to induce the deve lopment of corpora lutea and were hypophysectomized on Day 32. Beginning on Day 40, rats received twice-daily s.c. injections of either dexamethasone (dex; 200 mu g/rat/day) or vehicle (controls) and then were kilted on Day 4 4. Plasma 20 alpha-dihydroprogesterone, a major steroid produced by the cor pora lutea, was higher (p less than or equal to 0.01) in dex-treated than i n control rats (44.5 +/- 2.3 vs. 23.0 +/- 5.6 ng/ml). Dexamethasone treatme nt increased lipid droplets and lipid in the corpora lutea as revealed by e lectron microscopy and oil red O staining. Cholesterol esters were higher i n corpora lutea of dex-treated rats compared to controls (14.8 +/- 1.1 vs. 2.2 +/- 0.5 mu g/mg corpora lutea wet tissue, respectively; p less than or equal to 0.05). Another group of hypophysectomized rats was treated with ei ther a high or a lower dosage of corticosterone, both of which caused an el evation to > 2-fold of plasma 20 alpha-dihydroprogesterone concentration co mpared to controls. Glucocorticoid receptor protein (about 92 kDa) was dete cted in both luteal and nonluteal ovarian tissues in this animal model. The se effects of glucocorticoids and the presence of the glucocorticoid recept or raise the possibility of a physiological role for glucocorticoids in the rat corpus luteum.