Effects of Estradiol-17β on Oxytocin and Progesterone Release of the Bovine Corpus Luteum during the Estrous Cycle

概要

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The effects of estradiol-17β (E2) on progesterone (P4) and oxytocin (OT) release were examined. Corpora lutea (CL) were obtained from cows at different stages of the estrous cycle (days <5, 5-7, 8-12 and 15-18) and were implanted with an in vitro microdialysis system (MDS). A 3-h infusion with E2 (100 nmol/l, 1 nmol/l, 10 pmol/l and 100 fmol/l) shifted from no effect (days 5-7 and 8-12) to an inhibitory effect (days 15-18) on P4 release during the estrous cycle. E2 at all test doses was most stimulative on the release of OT during the early luteal phase (days 5-7) but continuously inhibited OT release from the middle to late phase of the estrous cycle. Contrary to results obtained from days 5-7, in CL on days <5, a stimulation (100 nmol/l) or inhibition (1 nmol/l and 10 pmol/l) of OT release was observed. In contrast, preexposure to a potent, specific estrogen antagonist (ICI 182, 780; 10 nmol/l, 3 h) during the early luteal phase (days 5-7) showed no effect on P4 release and completely impeded the stimulatory effect of E2 on the OT release. In addition, a 3-h preexposure perfusion of ICI 182, 780 prevented the inhibition of OT secretion by E2 on days 8-12. The results suggest that E2 acts directly and acutely on the secretory function of bovine CL in the MDS during the early luteal stage (days 5-7) of the estrous cycle and may act together with the released OT as a luteotropic factor.
日本繁殖生物学会の論文
1995-08-01