31 Dec

Endometrial Responsiveness to Oxytocin: DISCUSSION(2)

DISCUSSION(2)

Results for pregnant gilts differed markedly from those of cyclic ones, and they indicated that control of PGF2a secretion in pregnant gilts is not limited only to the level of the OTr but also resides at multiple sites subsequent to the OTr. The ability of ОТ to stimulate PI hydrolysis decreased between Days 12 and 16 in pregnant gilts and corresponded with decreased OTr density. Additionally, the ability of A1F4~ to stimulate PI hydrolysis was greater than that of ОТ on all days. Similarly, A1F4“ stimulated PGF2„ to a greater extent than did ОТ on Days 10-14. Collectively, these results indicated that some of the regulation of endometrial responsiveness occurred through changes in receptor density and/or coupling to Gq. ventolin inhaler

However, the ability of A1F4~ to stimulate PI hydrolysis was significantly decreased on Days 14-16 compared to Days 10-12, which showed that direct stimulation of Gq did not always result in maximal PI hydrolysis. Therefore, some regulation also occurred at the level of Gq and/or PLC. Further, A1F4, but not ОТ, activated Gq to increase PI hydrolysis on Day 16, whereas neither A1F4~ nor ОТ stimulated PGF2a secretion from endometrium of the same gilts. This indicated that it was not possible to activate the system by stimulating Gq and that control of PGF2ct secretion was also exerted subsequent to Gq in pregnant gilts. Presumably, the changes that occurred during early pregnancy in the present study were mediated through conceptus-secreted estradiol, because estradiol treatment suppressed endometrial responsiveness to ОТ and altered PGF2a secretion in a manner similar to that occurring in pregnant gilts. Potential sites of regulation include the IP3 receptor, IP3-sensitive calcium pools, protein kinase C, phospholipase A2, and membrane phospholipid stores of arachidonic acid.

Categories: Early Pregnancy
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