Chandrasekher Y A, Fortune J E
Department of Physiology, New York State College of Veterinary Medicine, Cornell University, Ithaca 14853.
Endocrinology. 1990 Aug;127(2):926-33. doi: 10.1210/endo-127-2-926.
Oxytocin (OT) is secreted during the final stages of bovine follicular development. To test OT's potential role as a regulator of follicular steroidogenesis, theca and granulosa cells were isolated from bovine preovulatory follicles 48 h after initiation of luteolysis with prostaglandin F2 alpha, and cultured with graded doses of OT (0, 0.5, 5, 50, and 500 mIU/ml). Granulosa cells were cultured with testosterone (0.5 microM) in either defined medium or medium containing 10% fetal bovine serum in the presence or absence of FSH (300 ng/ml); medium was collected and replaced daily for 5 days. In defined medium, oxytocin alone significantly increased progesterone production by granulosa cells (P less than 0.001) in a dose-dependent manner; over 5 days, doses of 0.5, 5, 50, and 500 mIU/ml OT caused 1.7-, 2.0-, 2.2-, and 2.6-fold increases. FSH enhanced progesterone 5-fold, but no dose of OT increased progesterone in the presence of FSH. OT also elevated progesterone in serum-containing medium (P less than 0.005), but the magnitude of its effects was lower (1.07-, 1.1-, 1.2-, and 1.4-fold increases with 0.5, 5, 50, and 500 mIU/ml OT). OT had little effect on estradiol secretion by granulosa cells cultured with or without FSH. To test the specificity of OT's effects on progesterone production by granulosa cells, granulosa cells were treated with graded doses of an OT antagonist (0, 1, 10, 100, and 1000 ng/ml) in the presence or absence of OT (5 and 50 mIU/ml). Progesterone production by granulosa cells in the presence of the antagonist alone was similar to production in control cultures. The stimulatory effects of 5 and 50 mIU OT were completely abolished in the presence of 100 or 1000 ng antagonist, respectively (P less than 0.01). Preparations of theca interna were cultured in defined medium with graded doses of OT (0, 0.5, 5, 50, and 500 mIU/ml) in the presence or absence of LH (300 ng/ml), with collection and replacement of medium at 3, 6, 12, 24, 48, and 72 h. LH alone increased both progesterone (12-fold) and androstenedione (4-fold) production over controls. However, no dose of OT significantly affected either progesterone or androstenedione production. These results show that OT stimulates progesterone production by granulosa cells, and thus, suggest that OT regulates steroidogenesis in bovine granulosa cells in vivo.
催产素（OT）在牛卵泡发育的最后阶段分泌。为了测试OT作为卵泡类固醇生成调节剂的潜在作用，在用前列腺素F2α启动黄体溶解48小时后，从牛排卵前卵泡中分离出卵泡膜细胞和颗粒细胞，并用不同剂量的OT（0、0.5、5、50和500 mIU/ml）进行培养。颗粒细胞在含有睾酮（0.5 microM）的限定培养基或含有10%胎牛血清的培养基中培养，添加或不添加促卵泡激素（FSH，300 ng/ml）；每天收集并更换培养基，持续5天。在限定培养基中，单独使用催产素能以剂量依赖的方式显著增加颗粒细胞的孕酮分泌（P < 0.001）；在5天内，0.5、5、50和500 mIU/ml的OT剂量分别使孕酮分泌增加了1.7倍、2.0倍、2.2倍和2.6倍。FSH使孕酮分泌增加了5倍，但在有FSH存在的情况下，任何剂量的OT都不会增加孕酮分泌。OT在含血清的培养基中也能提高孕酮水平（P < 0.005），但其作用幅度较小（0.5、5、50和500 mIU/ml的OT分别使孕酮分泌增加1.07倍、1.1倍、1.2倍和1.4倍）。OT对添加或不添加FSH培养的颗粒细胞的雌二醇分泌影响很小。为了测试OT对颗粒细胞孕酮分泌作用的特异性，在添加或不添加OT（5和50 mIU/ml）的情况下，用不同剂量的OT拮抗剂（0、1、10、100和1000 ng/ml）处理颗粒细胞。单独使用拮抗剂时颗粒细胞的孕酮分泌与对照培养相似。在分别存在100或1000 ng拮抗剂时，5和50 mIU OT的刺激作用完全被消除（P < 0.01）。将内膜细胞制剂在限定培养基中培养，添加不同剂量的OT（0、0.5、5、50和500 mIU/ml），添加或不添加黄体生成素（LH，300 ng/ml），在3、6、12、24、48和72小时收集并更换培养基。单独使用LH使孕酮（增加12倍）和雄烯二酮（增加4倍）的分泌量超过对照组。然而，任何剂量的OT对孕酮或雄烯二酮的分泌均无显著影响。这些结果表明，OT刺激颗粒细胞产生孕酮，因此，提示OT在体内调节牛颗粒细胞的类固醇生成。
