Hazzard T M, Pinckard K L, Stormshak F
Department of Animal Sciences, Oregon State University, Corvallis 97331-6702, USA.
Biol Reprod. 1998 Jul;59(1):105-10. doi: 10.1095/biolreprod59.1.105.
Three experiments were conducted, the objectives of which were to 1) examine the effects of exogenous estradiol (E2) and progesterone (P4) on uterine concentrations of oxytocin receptors (OTR) and OTR mRNA, as well as the effect of exogenous P4 on progesterone receptors (PR) during the late luteal phase of the cycle, and 2) ascertain whether chronic E2 treatment of ewes during the cycle would alter prostaglandin F2alpha (PGF2alpha)-induced secretion of luteal oxytocin (OT). In experiment 1, 15 ewes were assigned to a control (n = 5; 2 ml corn oil [CO] s.c. on Days 4-14 of the estrous cycle) and two treatment groups (n = 5 each) receiving either 250 microg E2 s.c. (Days 4-14) or 10 mg P4 s.c. (CO on Days 4-10 and P4 on Days 11-14). Endometria and corpora lutea were removed on Day 15 of the cycle. Mean luteal weights were greater in treated than in control ewes (p < 0.05). Endometrial concentrations of OTR and OTR mRNA were significantly greater in control than in E2- or P4-treated ewes. In experiment 2, five ewes each were treated s.c. with CO or 10 mg P4 on Days 11-14 of the cycle; endometria were then removed on Day 15 for PR assay. Endometrial concentration of PR did not differ between groups. Experiment 3 consisted of 20 ewes assigned to four groups in a 2 x 2 factorial arrangement. Treatment consisted of two dosages of E2 (0 or 250 microg/day) in 2 ml CO and two dosages of PGF2alpha analogue (0 or 125 microg Estrumate). All ewes were injected s.c. with E2 or CO for 11 days as described for experiment 1. On Day 15, all ewes received an i.v. injection of PGF2alpha or saline (Time 0); then jugular blood was collected at frequent intervals for analysis of serum concentrations of OT. PGF2alpha induced a release of OT in control and E2-treated ewes (p < 0.05) compared to the value in saline-treated ewes. Collectively, these data suggest that in cycling ewes, exposure of the uterus to increased concentrations of E2 or P4 causes down-regulation of OTR as a consequence of suppression of the OTR gene. Chronic E2 treatment of ewes during the cycle does not act directly on the ovary to alter the stores of luteal OT.
进行了三项实验，其目的在于：1）研究外源性雌二醇（E2）和孕酮（P4）对发情周期黄体后期子宫中催产素受体（OTR）及其mRNA浓度的影响，以及外源性P4对孕酮受体（PR）的影响；2）确定在发情周期中对母羊进行慢性E2处理是否会改变前列腺素F2α（PGF2α）诱导的黄体催产素（OT）分泌。在实验1中，15只母羊被分为一个对照组（n = 5；在发情周期的第4 - 14天皮下注射2 ml玉米油[CO]）和两个处理组（每组n = 5），分别在第4 - 14天皮下注射250 μg E2，或在第4 - 10天皮下注射CO，第11 - 14天皮下注射10 mg P4。在周期的第15天切除子宫内膜和黄体。处理组母羊的平均黄体重量高于对照组（p < 0.05）。对照组母羊子宫内膜中OTR及其mRNA的浓度显著高于E2或P4处理组。在实验2中，每组5只母羊在周期的第11 - 14天皮下注射CO或10 mg P4；然后在第15天切除子宫内膜进行PR检测。两组之间子宫内膜PR浓度无差异。实验3由20只母羊组成，按2×2析因设计分为四组。处理包括在2 ml CO中两种剂量的E2（0或250 μg/天）和两种剂量的PGF2α类似物（0或125 μg氯前列醇）。所有母羊如实验1所述皮下注射E2或CO，持续11天。在第15天，所有母羊静脉注射PGF2α或生理盐水（时间0）；然后每隔一段时间采集颈静脉血，分析血清OT浓度。与注射生理盐水的母羊相比，PGF2α诱导对照组和E2处理组母羊释放OT（p < 0.05）。总体而言，这些数据表明，在发情周期的母羊中，子宫暴露于浓度升高的E2或P4会导致OTR基因受抑制，从而使OTR下调。在发情周期中对母羊进行慢性E2处理不会直接作用于卵巢来改变黄体OT的储备。
