05 Jan

Endometrial Responsiveness to Oxytocin: DISCUSSION(7)

The current study supported the proposal that reduced endocrine secretion of PGF2a resulting from conceptus secretion of estradiol during maternal recognition of pregnancy in pigs involved reduced responsiveness to ОТ. Although no differences existed for OTr binding characteristics, PI hydrolysis, PGF2a secretion, and progesterone production between pregnant and cyclic gilts on Day 10, and only modest differences were noted by Days 12-14 in experiment 1, treatment of endometrium from cyclic gilts with ОТ on Day 16 resulted in greater PI hydrolysis and PGF2a secretion. Endometrial OTr density also decreased in pregnant gilts after Day 12 and tended to be lower than for cyclic gilts on Day 16. Results of the current study are also consistent with previous studies in that endometrium from cyclic gilts during the luteolytic period was more responsive than that from pregnant gilts. However, we were unable to demonstrate increased responsiveness to ОТ before decreased progesterone production in cyclic gilts as previously reported. buy asthma inhaler

Although the 100-nM concentration of ОТ used to treat endometrium in experiment 1 was substantially higher than was reported to be present in the peripheral circulation of sows during late diestrus, we previously showed that endometrium from cyclic pigs responded to 10 nM ОТ with increased PGF2a secretion. Further, it was recently reported that ОТ was expressed by pig endometrium and secreted in copious quantities into the uterine lumen. This would expose the endometrium to ОТ concentrations ranging from 0.8 to 2.4 nM in cyclic pigs and 12.7 to 121.5 nM in pregnant pigs. However, these concentrations probably underestimate the amount of ОТ within the uterus of pigs because they were based upon the assumptions that 100% of the ОТ present within each uterine horn was recovered with 30 ml flush medium and that the volume of free-standing fluid within the pig uterus was approximately 5 ml, which is likely to be an overestimate.

Categories: Early Pregnancy
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