Davies K L, Bartlewski P M, Epp T, Duggavathi R, Barrett D M W, Bagu E T, Cook S J, Rawlings N C
Department of Veterinary Biomedical Sciences, WCVM, University of Saskatchewan, 52 Campus Drive, Saskatoon, Sask., Canada S7N 5B4.
Theriogenology. 2006 Jul 15;66(2):251-9. doi: 10.1016/j.theriogenology.2005.08.027. Epub 2005 Dec 5.
In a previous study in our laboratory, treatment of non-prolific Western White Face (WWF) ewes with PGF(2 alpha) and intravaginal sponges containing medroxyprogesterone acetate (MAP) on approximately Day 8 of a cycle (Day 0 = first ovulation of the interovulatory interval) resulted in ovulations during the subsequent 6 days when MAP sponges were in place. Two experiments were performed on WWF ewes during anestrus to allow us to independently examine if such ovulations were due to the direct effects of PGF(2 alpha) on the ovary or to the effects of a rapid decrease in serum concentrations of progesterone at PGF(2 alpha)-induced luteolysis. Experiment 1: ewes fitted with MAP sponges for 6 days (n = 12) were injected with PGF(2 alpha) (n = 6; 15 mg im), or saline (n = 6) on the day of sponge insertion. Experiment 2: ewes received progesterone-releasing subcutaneous implants (n = 6) or empty implants (n = 5) for 5 days. Six hours prior to implant removal, all ewes received a MAP sponge, which remained in place for 6 days. Ewes from both experiments underwent ovarian ultrasonography and blood sampling once daily for 6 days before and twice daily for 6 days after sponge insertion. Additional blood samples were collected every 4 h during sponge treatment. Experiment 1: 4-6 (67%) PGF(2 alpha)-treated ewes ovulated approximately 1.5 days after PGF(2 alpha) injection; these ovulations were not preceded by estrus or a preovulatory surge release of LH, and resulted in transient corpora hemorrhagica (CH). The growth phase was longer (P < 0.05) and the growth rate slower (P < 0.05) in ovulating versus non-ovulating follicles in PGF(2 alpha)-treated ewes. Experiment 2: in ewes given progesterone implants, serum progesterone concentrations reached a peak (1.7 2 ng/mL; P < 0.001) on the day of implant removal and decreased to basal concentrations (<0.17 ng/mL; P < 0.001) within 24 h of implant removal. No ovulations occurred in either the treated or the control ewes. We concluded that ovulations occurring after PGF(2 alpha) injection, in the presence of a MAP sponge, could be due to a direct effect of PGF(2 alpha) at the ovarian level, rather than a sudden decline in circulating progesterone concentrations.
在我们实验室之前的一项研究中，在一个周期的大约第8天（第0天 = 排卵间期的第一次排卵），用前列腺素F2α（PGF2α）和含醋酸甲羟孕酮（MAP）的阴道海绵栓处理不发情的西部白面（WWF）母羊，当MAP海绵栓在位时，在随后6天内出现了排卵。在休情期对WWF母羊进行了两项实验，以使我们能够独立研究这种排卵是由于PGF2α对卵巢的直接作用，还是由于PGF2α诱导黄体溶解时血清孕酮浓度迅速下降的影响。实验1：安装MAP海绵栓6天的母羊（n = 12）在插入海绵栓当天注射PGF2α（n = 6；15 mg，肌肉注射）或生理盐水（n = 6）。实验2：母羊接受释放孕酮的皮下植入物（n = 6）或空植入物（n = 5）5天。在取出植入物前6小时，所有母羊都接受一个MAP海绵栓，该海绵栓在位6天。两个实验中的母羊在插入海绵栓前6天每天进行一次卵巢超声检查和采血，插入海绵栓后6天每天进行两次采血。在海绵栓处理期间每4小时采集一次额外的血样。实验1：4 - 6只（67%）接受PGF2α处理的母羊在注射PGF2α后约1.5天排卵；这些排卵之前没有发情或促黄体生成素（LH）的排卵前激增释放，并且导致了短暂的出血性黄体（CH）。在接受PGF2α处理的母羊中，排卵卵泡与未排卵卵泡相比，生长阶段更长（P < 0.05）且生长速度更慢（P < 0.05）。实验2：在接受孕酮植入物的母羊中，血清孕酮浓度在取出植入物当天达到峰值（1.7±2 ng/mL；P < 0.001），并在取出植入物后24小时内降至基础浓度（<0.17 ng/mL；P < 0.001）。处理组和对照组母羊均未排卵。我们得出结论，在存在MAP海绵栓的情况下，注射PGF2α后发生的排卵可能是由于PGF2α在卵巢水平的直接作用，而不是循环孕酮浓度的突然下降。
