Taya K, Greenwald G S
Biol Reprod. 1982 Dec;27(5):1090-101. doi: 10.1095/biolreprod27.5.1090.
To determine the mechanisms responsible for the suppression of follicular development in the lactating rat, in vivo and in vitro determinations of steroid and peptide hormones combined with the histological size-distribution of ovarian follicles were compared among three groups of post-parturient rats nursing 0, 2 or 8 pups. From Days 4 to 12 (day of parturition = Day 0 of lactation), in dams nursing 8 pups, follicles larger than 401 microns in diameter were absent, whereas follicles of this size were always present in mothers nursing 0 or 2 pups. The in vitro production rates of estradiol-17 beta (E2) and testosterone (T) by nonluteal ovarian tissues (NLO) were consistently lower in dams nursing 8 pups than in mothers nursing 0 or 2 young, correlating with the histological observations. Serum E2 and 20 alpha-dihydroprogesterone (20 alpha-OHP) in rats with 8 pups were significantly lower, whereas serum progesterone (P) was significantly increased compared to the values in dams nursing 0 or 2 pups. In mothers nursing 8 pups, the corpora lutea (CL) of lactation, formed at postpartum ovulation, produced in vitro significantly greater amounts of P but significantly lesser amount of E2 compared to the other groups. Serum luteinizing hormone (LH) was consistently lower in dams nursing 8 pups than in dams nursing 0 or 2 pups. There was, however, no significant difference in serum follicle-stimulating hormone (FSH) among the 3 types of postparturient rats. Throughout lactation serum values of FSH were within the range of diestrous levels during the estrous cycle. Serum levels of prolactin (Prl) in dams nursing 8 pups were strikingly higher compared to dams nursing 2 pups. The administration of small doses of human chorionic gonadotropin (hCG) or ovine LH twice daily from Days 2 to 5 to lactating rats nursing 8 pups induced the maturation of follicles capable of ovulating. These findings indicate that during the first half of lactation the strong suckling stimulus reduces serum LH directly or indirectly via high levels of serum Prl and P, which in turn inhibit follicular maturation. During the second half of lactation, the suckling stimulus wanes, Prl and P decline and serum LH recovers to basal cyclic values which are reflected in the initiation of follicular maturation.
为了确定导致哺乳期大鼠卵泡发育受抑制的机制，我们比较了三组分别哺育0只、2只或8只幼崽的产后大鼠体内和体外类固醇及肽类激素的测定结果，并结合卵巢卵泡的组织学大小分布情况进行分析。从第4天至第12天（分娩日 = 哺乳期第0天），在哺育8只幼崽的母鼠中，直径大于401微米的卵泡不存在，而在哺育0只或2只幼崽的母鼠中，这种大小的卵泡总是存在。与组织学观察结果相关，哺育8只幼崽的母鼠中非黄体卵巢组织（NLO）体外雌二醇 - 17β（E2）和睾酮（T）的产生率始终低于哺育0只或2只幼崽的母鼠。与哺育0只或2只幼崽的母鼠相比，哺育8只幼崽的大鼠血清E2和20α - 二氢孕酮（20α - OHP）显著降低，而血清孕酮（P）显著升高。在哺育8只幼崽的母鼠中，产后排卵时形成的哺乳期黄体（CL）体外产生的P量显著高于其他组，但E2量显著低于其他组。哺育8只幼崽的母鼠血清促黄体生成素（LH）始终低于哺育0只或2只幼崽的母鼠。然而，三种产后大鼠血清促卵泡生成素（FSH）之间没有显著差异。在整个哺乳期，FSH的血清值处于发情周期间情期水平范围内。与哺育2只幼崽的母鼠相比，哺育8只幼崽的母鼠血清催乳素（Prl）水平显著更高。从第2天至第5天，每天给哺育8只幼崽的哺乳期大鼠注射小剂量人绒毛膜促性腺激素（hCG）或羊LH两次，可诱导能够排卵的卵泡成熟。这些发现表明，在哺乳期的前半期，强烈的哺乳刺激通过高水平的血清Prl和P直接或间接降低血清LH，进而抑制卵泡成熟。在哺乳期的后半期，哺乳刺激减弱，Prl和P下降，血清LH恢复到基础周期值，这反映在卵泡成熟的开始。
