Ziecik A, Tilton J E, Espana F, Weigl R
J Anim Sci. 1987 Apr;64(4):1134-43. doi: 10.2527/jas1987.6441134x.
The influence of varying doses of human chorionic gonadotropin (hCG) on the preovulatory luteinizing hormone (LH) surge, estradiol-17 beta (E2) and progesterone (P4) was studied in synchronized gilts. Altrenogest (AT) was fed (15 mg X head-1 X d-1) to 24 cyclic gilts for 14 d. Pregnant mares serum gonadotropin (PMSG; 750 IU) was given im on the last day of AT feeding. The gilts were then assigned to one of four groups (n = 6): saline (I), 500 IU hCG (II), 1,000 IU hCG (III) and 1,500 IU hCG (IV). Human chorionic gonadotropin or saline was injected im 72 h after PMSG. No differences in ovulation rate or time from last feeding of AT to occurrence of estrus were observed. All gilts in Groups I and II expressed a preovulatory LH surge compared with only four of six and three of six in Groups III and IV, respectively. All groups treated with hCG showed a rapid drop (P less than .01) in plasma levels of E2 11, 17, 23 h after hCG injection when compared with the control group (35 h). The hCG-treated gilts exhibited elevated P4 concentrations 12 h earlier than the control group (3.1 +/- .5, 3.4 +/- .72, 3.1 +/- .10 ng/ml in groups II, III and IV at 60 h post-hCG vs .9 +/- .08 ng/ml in group I; P less than .05). These studies demonstrate that injections of ovulatory doses of hCG (500 to 1,500 IU) had three distinct effects on events concomitant with occurrence of estrus in gilts: decreased secretion of E2 immediately after hCG administration, failure to observe a preovulatory LH surge in some treated animals and earlier production of P4 by newly developed corpora lutea.
在同步发情的后备母猪中研究了不同剂量的人绒毛膜促性腺激素（hCG）对排卵前促黄体生成素（LH）峰、雌二醇-17β（E2）和孕酮（P4）的影响。给24头处于发情周期的后备母猪饲喂烯丙孕素（AT，15mg/头·天），持续14天。在饲喂AT的最后一天，肌肉注射孕马血清促性腺激素（PMSG，750IU）。然后将这些后备母猪分为四组（每组n = 6）：生理盐水组（I）、500IU hCG组（II）、1000IU hCG组（III）和1500IU hCG组（IV）。在注射PMSG 72小时后，肌肉注射人绒毛膜促性腺激素或生理盐水。未观察到排卵率以及从最后一次饲喂AT到发情出现的时间存在差异。与III组和IV组中分别只有4/6和3/6的后备母猪出现排卵前LH峰相比，I组和II组中的所有后备母猪均出现了排卵前LH峰。与对照组（35小时）相比，所有接受hCG处理的组在注射hCG后11、17、23小时时血浆E2水平均迅速下降（P < 0.01）。接受hCG处理的后备母猪比对照组提前12小时出现P4浓度升高（hCG注射后60小时，II组、III组和IV组的P4浓度分别为3.1±0.5、3.4±0.72、3.1±0.10ng/ml，而I组为0.9±0.08ng/ml；P < 0.05）。这些研究表明，注射排卵剂量的hCG（500至1500IU）对后备母猪发情相关事件有三种不同影响：hCG给药后立即降低E2分泌、部分处理动物未观察到排卵前LH峰以及新形成的黄体更早产生P4。
