UTERINE ESTRADIOL AND PROGESTERONE-RECEPTOR CONCENTRATION, ACTIVITIESOF CERTAIN ANTIOXIDANT ENZYMES AND DEHYDROGENASES AND HISTOARCHITECTURE IN RELATION TO TIME OF SECRETION OF NIDATORY ESTROGEN AND HIGH ENDOMETRIAL SENSITIVITY IN RAT

Alterations in uterine nuclear and cytosolic estradiol (ER) and proges terone (PR) receptor concentration, activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glucose-6-phosphate dehydrog enase (G-6-PDH) and lactate dehydrogenase (LDH), surface and transmiss ion electron microscopy and histology in relation to the time of secre tion of nidatory estrogen and the onset of endometrial sensitivity in the rat were investigated. A significant increase in plasma estradiol (E(2)) concentration in control rats was observed at 22.00 h on day 4 post-coitum, whereas progesterone (P) concentration increased at 17.00 h on day 4 and was maintained until 17.00 h on day 5. The period of h igh endometrial sensitivity (10.00 h on day 5) was characterized by el evated uterine cytosolic ER and nuclear and cytosolic PR concentration and POD activity, low columnar luminal epithelium with undulating sur face and intercellular membranes, covered with short microvilli and pi nopods, and containing numerous electron-transparent apical vesicles, mitochondria, polyribosomes, rough (RER) and smooth (SER) endoplasmic reticulum, well developed Golgi, few lysosomes and lipid droplets and loose edematous antimesometrial stroma. Inhibition in endometrial sens itivity by post-coital centchroman was associated with a marked deplet ion in uterine cytosolic ER and an increase in nuclear ER concentratio n, a decrease in POD and G-6-PDH activities, compact fibroblastic stro ma, an increase in luminal epithelial cell height with decreased RER, SER, polyribosomes, Golgi, straightening of intercellular membranes, r educed surface undulations and absence of pinopods. Electron-transpare nt vesicles appeared flattened and clumped in the apical portion of ce lls, tight junctions were more prominent and lipid droplets were trans lucent. Nuclear and cytosolic PR and the pattern of secretion or plasm a E(2) and P remained unaffected. CAT, SOD and LDH activities, althoug h high throughout pre-implantation, did not vary in relation to the se cretion of nidatory estrogen, endometrial sensitivity or centchroman t reatment. Copyright (C) 1996 Elsevier Science Ltd.