Eissa H M, el-Belely M S
Department of Surgery and Theriogenology, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt.
Br Vet J. 1990 Jan-Feb;146(1):24-9. doi: 10.1016/0007-1935(90)90072-B.
Blood samples were taken thrice weekly for 2 weeks from 33 pregnant cows in nine groups, 1 month apart, and twice daily for 8 days commencing 1 week before parturition from eight cows. Plasma progesterone and total oestrogens were quantified by validated radioimmunoassays and total corticosteroids by a competitive protein binding technique. During the first 3 months of pregnancy, no remarkable changes were observed for the three hormones studied. From the fourth month on, concentrations of progesterone and total corticosteroids decreased significantly (P less than 0.05) and remained fairly constant until the ninth month. Values of total oestrogens increased significantly (P less than 0.05) from the fourth to the sixth month and thereafter remained unchanged. In the periparturient cows, progesterone levels decreased linearly (P less than 0.01) during the 3 days preceding delivery. Concentrations of total oestrogens rose sharply from day -5 and peaked at calving. Values of total corticosteroids increased dramatically on the sixth day and also at 24 hours before parturition. These results suggest that, contrary to earlier studies, plasma corticosteroids could have a primary key role for triggering parturition in cows.
从9个组的33头怀孕母牛中，每隔1个月每周采集3次血样，共采集2周；从8头母牛中，在分娩前1周开始每天采集2次血样，共采集8天。采用经过验证的放射免疫分析法对血浆孕酮和总雌激素进行定量分析，采用竞争性蛋白结合技术对总皮质类固醇进行定量分析。在怀孕的前3个月，所研究的三种激素均未观察到明显变化。从第4个月开始，孕酮和总皮质类固醇的浓度显著下降（P<0.05），并一直保持相当稳定，直到第9个月。总雌激素的值从第4个月到第6个月显著增加（P<0.05），此后保持不变。在围产期母牛中，孕酮水平在分娩前3天呈线性下降（P<0.01）。总雌激素的浓度从第-5天开始急剧上升，并在产犊时达到峰值。总皮质类固醇的值在第6天以及分娩前24小时也显著增加。这些结果表明，与早期研究相反，血浆皮质类固醇可能在引发母牛分娩中起主要关键作用。
