Kombé A, Sirois J, Goff A K
Centre de Recherche en Reproduction Animale, Faculté de Médecine Vétérinaire, Université de Montréal, 3200 Rue Sicotte, St-Hyacinthe, Que., Canada J2S 7C6.
Steroids. 2003 Sep;68(7-8):651-8. doi: 10.1016/s0039-128x(03)00094-1.
Estradiol (E2), progesterone (P4), and oxytocin (OT) are important for the initiation of luteolysis in ruminants but the mechanisms involved are still poorly understood. The objective of this study was to determine if duration of exposure of bovine endometrial epithelial cells to P4 affected the response of the cells to E2. Endometrial epithelial cells, from cows at Days 1-3 of the estrous cycle, were cultured for 10, 17, and 21 days in the presence or absence of P4 (100 ng ml(-1)). After culture, each group of cells was incubated for a further 6, 12, 24 or 48 h with or without E2 (100 pg ml(-1)) and then incubated for 6 h with different doses of OT (2, 20, and 200 ng ml(-1)). E2 enhanced OT-stimulated PGF2 alpha secretion in cells cultured with P4 for 17 or 21 days, with a maximum effect after 24-h exposure, but not in cells cultured with P4 for 10 days. To determine the mechanism of action of E2, COX-1 and COX-2 were measured by Western blotting and OTR number was measured by saturation analysis. OT increased COX-2 (P<0.05), but there was no significant effect of E2 on the expression of either COX-1 or COX-2. E2 did, however, increase (P<0.001) the OTR number in cells cultured with P4 for 21 days, whereas it inhibited OTR in cells cultured for 10 days. These data show that E2 can stimulate PGF2 alpha secretion by increasing OTR expression in bovine endometrial cells in vitro, but only after exposure to P4.
雌二醇（E2）、孕酮（P4）和催产素（OT）对反刍动物黄体溶解的起始过程很重要，但其中涉及的机制仍知之甚少。本研究的目的是确定牛子宫内膜上皮细胞暴露于P4的持续时间是否会影响细胞对E2的反应。从发情周期第1 - 3天的奶牛获取子宫内膜上皮细胞，在有或无P4（100 ng ml(-1)）的情况下培养10、17和21天。培养后，每组细胞在有或无E2（100 pg ml(-1)）的情况下再孵育6、12、24或48小时，然后与不同剂量的OT（2、20和200 ng ml(-1)）一起孵育6小时。E2增强了在含P4条件下培养17或21天的细胞中OT刺激的前列腺素F2α分泌，在暴露24小时后达到最大效应，但在含P4条件下培养10天的细胞中未出现此现象。为确定E2的作用机制，通过蛋白质免疫印迹法检测COX - 1和COX - 2，通过饱和分析检测催产素受体（OTR）数量。OT增加了COX - 2（P<0.05），但E2对COX - 1或COX - 2的表达均无显著影响。然而，E2确实增加了（P<0.001）在含P4条件下培养21天的细胞中的OTR数量，而在培养10天的细胞中它抑制了OTR。这些数据表明，E2可通过增加体外培养的牛子宫内膜细胞中的OTR表达来刺激前列腺素F2α分泌，但前提是细胞先暴露于P4。
