Sirois J, Kimmich T L, Fortune J E
Division of Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York.
Endocrinology. 1990 Nov;127(5):2423-30. doi: 10.1210/endo-127-5-2423.
Ovulation in mares is preceded by a long and variable estrous period. The differentiation of equine preovulatory follicles with respect to steroidogenic capacity and responsiveness to equine gonadotropins was studied by culturing pieces of follicle wall (FW = theca + attached granulosa cells) from preovulatory follicles isolated during late diestrus (day 14 of cycle, n = 5 mares), early estrus (1st-2nd day of estrus, n = 6) or late estrus (4th or 5th day of estrus, n = 6). FW was cultured with or without equine LH, FSH, LH + FSH, or CG (10 or 100 ng/ml) and medium was collected and replaced at 3, 6, 12, 24, 48, and 72 h of culture. Follicular fluid from presumptive ovulatory follicles and medium from FW cultures were assayed for progesterone, androstenedione, and estradiol-17 beta. The cumulative secretion of all three steroids after 72 h of culture was significantly lower in FW isolated during late diestrus (P less than 0.05) as compared with early or late estrus. Maximal progesterone secretion was observed with FW from late estrus whereas maximal androstenedione and estradiol secretion in vitro occurred with FW from early estrus. In contrast to results obtained in vitro, concentrations of progesterone in follicular fluid were not different among stages of follicular development, and concentrations of androstenedione and estradiol in follicular fluid were maximal in late estrous follicles. Equine gonadotropins had their greatest stimulatory effect on steroidogenesis with FW obtained during late diestrus. As compared with controls, the addition of LH, FSH, or LH + FSH (100 ng/ml) increased progesterone secretion by FW from late diestrus (48x, 64x, and 58x, respectively, P less than 0.01), early estrus (24x, 32x, and 36x, P less than 0.01) and late estrus (9x, 9x, and 9x, P less than 0.01). Equine LH and FSH also increased androstenedione secretion by follicles obtained during diestrus and estrus. In contrast, estradiol secretion showed a more rapid loss in responsiveness to gonadotropin stimulation, with both LH and FSH stimulating estradiol secretion by FW from late diestrous follicles (P less than 0.01), but neither stimulating FW from early or late estrous follicles. Overall, eCG was a less potent stimulator of steroidogenesis in vitro than LH and FSH.(ABSTRACT TRUNCATED AT 400 WORDS)
母马排卵前有一个漫长且多变的发情期。通过培养来自在发情后期（周期第14天，n = 5匹母马）、发情早期（发情第1 - 2天，n = 6匹）或发情后期（发情第4或5天，n = 6匹）分离出的排卵前卵泡的卵泡壁碎片（FW = 卵泡膜 + 附着的颗粒细胞），研究了马排卵前卵泡在类固醇生成能力和对马促性腺激素反应性方面的差异。FW在添加或不添加马LH、FSH、LH + FSH或CG（10或100 ng/ml）的情况下进行培养，在培养3、6、12、24、48和72小时时收集并更换培养基。检测推测排卵卵泡的卵泡液以及FW培养物的培养基中的孕酮、雄烯二酮和雌二醇 - 17β。培养72小时后，与发情早期或后期相比，发情后期分离出的FW中所有三种类固醇的累积分泌量显著较低（P < 0.05）。发情后期的FW观察到最大孕酮分泌，而体外最大雄烯二酮和雌二醇分泌发生在发情早期的FW。与体外结果相反，卵泡发育各阶段卵泡液中的孕酮浓度无差异，发情后期卵泡的卵泡液中雄烯二酮和雌二醇浓度最高。马促性腺激素对发情后期获得的FW的类固醇生成具有最大刺激作用。与对照相比，添加LH、FSH或LH + FSH（100 ng/ml）使发情后期FW的孕酮分泌增加（分别为48倍、64倍和58倍，P < 0.01），发情早期FW的孕酮分泌增加（24倍、32倍和36倍，P < 0.01），发情后期FW的孕酮分泌增加（9倍、9倍和9倍，P < 0.01）。马LH和FSH也增加了发情期和发情后期获得的卵泡的雄烯二酮分泌。相反，雌二醇分泌对促性腺激素刺激的反应性丧失更快，LH和FSH均刺激发情后期卵泡的FW分泌雌二醇（P < 0.01），但均不刺激发情早期或后期卵泡的FW分泌雌二醇。总体而言，在体外，eCG对类固醇生成的刺激作用比LH和FSH弱。（摘要截断于400字）
