| Abstract: | Estradiol stimulation and progesterone inhibition of human uterine PGF2 alpha production were studied using in vitro preparations of endometrial tissue and cells. Measurement of PGF2 alpha levels in media from primary cultures of glandular epithelia and stoma revealed that basal outputs were similar in both cell types but could be increased by estradiol only in epithelial cells. Tamoxifen (Tam) and trans-4-hydroxy tamoxifen (OHTam) did not affect basal PGF2 alpha outputs by secretory endometrium in organ culture and by monolayer cultures of epithelial cells, but counteracted the stimulatory effects of estradiol in both systems. The almost pure antiestrogenic activity exhibited by OHTam was at least 10 times greater than that of Tam, suggesting that the estrogen-stimulated increases in uterine PGF2 alpha output are mediated by specific estrogen receptors. Fragments of endometrium also released lipocortin, a phospholipase A2-inhibiting protein believed to mediate inhibitory effects of glucocorticoids on prostaglandin production in several types of cells. Although dexamethasone increased lipocortin and decreased PGF2 alpha output in secretory endometria in vitro, progesterone inhibited both lipocortin and PGF2 alpha output. The mechanisms by which P inhibits PGF2 alpha production remain to be elucidated. |
