Liu J, Sirois J
Centre de recherche en reproduction animale, Département de biomédecine vétérinaire, Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada.
Biol Reprod. 1998 Jun;58(6):1527-32. doi: 10.1095/biolreprod58.6.1527.
Under physiological conditions, prostaglandin G/H synthase-2 (PGHS-2) is induced in bovine preovulatory follicles by the endogenous surge of gonadotropins. To characterize the pattern of follicular PGHS-2 expression during superovulation in cattle, heifers were treated with exogenous FSH and ovulation was induced with hCG. Animals were ovariectomized 0, 18, and 24 h post-hCG, and extracts of follicles > or = 6 mm were analyzed by Western blotting. Follicular fluid concentrations of prostaglandin (PG) E2, PGF2alpha, progesterone, and estradiol-17beta were determined by RIAs, and the morphology of the cumulus oocyte complex was examined. Results showed that PGHS-2 protein was absent in all follicles isolated at 0 h post-hCG (n = 119) and in small follicles (6 to < 8 mm) isolated between 0 and 24 h post-hCG (n = 27 follicles). In contrast, 12.3% of medium (8 to < 10 mm) and 43.7% of large (> or = 10 mm) follicles were PGHS-2-positive at 18 h post-hCG, and these percentages rose at 24 h to 45.9% and 91.0% in medium and large follicles, respectively (p < 0.05). Follicular fluid concentrations of PGE2 and PGF2alpha were low in follicles isolated at 0 h and increased only in PGHS-2-positive follicles isolated 24 h post-hCG (p < 0.05). Concentrations of progesterone and estradiol-17beta at 0 h were 28.2 +/- 5.8 and 291.8 +/- 13.0 ng/ml, respectively, and a shift from estradiol-17beta to progesterone dominance (luteinization) occurred at 24 h post-hCG only in PGHS-2-positive follicles. Also, expansion of the cumulus oocyte complex was detected at 24 h post-hCG only in PGHS-2-positive follicles. Lack of PGHS-2 induction in follicles of ovulatory size (> 8 mm) was associated with an apparent failure to respond to hCG (absence of luteinization and cumulus expansion). Collectively, these results demonstrate the presence of a time- and follicle size-dependent induction of PGHS-2 in bovine follicles during superovulatory treatment and suggest that PGHS-2 expression can be used as a marker for follicular commitment to ovulation during ovarian hyperstimulation protocols.
在生理条件下，促性腺激素的内源性激增可诱导牛排卵前卵泡中前列腺素G/H合酶-2（PGHS-2）的产生。为了确定牛超数排卵期间卵泡PGHS-2表达的模式，用外源性促卵泡素（FSH）处理小母牛，并用人类绒毛膜促性腺激素（hCG）诱导排卵。在注射hCG后0、18和24小时对动物进行卵巢切除，对直径≥6mm的卵泡提取物进行蛋白质免疫印迹分析。通过放射免疫分析法（RIA）测定卵泡液中前列腺素（PG）E2、PGF2α、孕酮和雌二醇-17β的浓度，并检查卵丘卵母细胞复合体的形态。结果显示，在注射hCG后0小时分离的所有卵泡（n = 119）以及在注射hCG后0至24小时分离的小卵泡（6至<8mm，n = 27个卵泡）中均未检测到PGHS-2蛋白。相反，在注射hCG后18小时，12.3%的中等大小卵泡（8至<10mm）和43.7%的大卵泡（≥10mm）为PGHS-2阳性，在24小时时，中等大小卵泡和大卵泡中的这些百分比分别升至45.9%和91.0%（p<0.05）。在注射hCG后0小时分离的卵泡中，卵泡液中PGE2和PGF2α的浓度较低，且仅在注射hCG后24小时分离的PGHS-2阳性卵泡中升高（p<0.05）。0小时时孕酮和雌二醇-17β的浓度分别为28.2±5.8和291.8±13.0ng/ml，仅在PGHS-2阳性卵泡中，注射hCG后24小时出现了从雌二醇-17β占主导向孕酮占主导的转变（黄体化）。此外，仅在PGHS-2阳性卵泡中，注射hCG后24小时检测到卵丘卵母细胞复合体扩张。排卵大小的卵泡（>8mm）中缺乏PGHS-2诱导与对hCG无明显反应（无黄体化和卵丘扩张）有关。总体而言，这些结果表明在超数排卵处理期间，牛卵泡中存在时间和卵泡大小依赖性的PGHS-2诱导，并表明PGHS-2表达可作为卵巢过度刺激方案中卵泡排卵倾向的标志物。
