Padmanabhan V, Convey E M, Roche J F, Ireland J J
Endocrinology. 1984 Oct;115(4):1332-40. doi: 10.1210/endo-115-4-1332.
The objectives of this study were to develop a bioassay for measuring inhibin bioactivity in untreated samples of bovine follicular fluid (BFF) and then examine changes in inhibin bioactivity in ovulatory and atretic follicles and utero-ovarian venous blood during the periovulatory period in heifers. A rat pituitary cell culture system was used to bioassay inhibin-like activity. Addition of 0.005 to 1 microliter untreated (whole), unfiltered charcoal-stripped, or filtered whole BFF to pituitary cultures caused a linear suppression of LHRH-induced FSH release but had no effect on LH secretion. Steroids in BFF did not suppress FSH secretion, since removal of steroids from BFF with charcoal did not remove the FSH-suppressive activity in BFF. Addition of ether extracts of BFF caused a slight but nonparallel suppression of FSH secretion; however, heating these extracts removed most of this suppressive activity. Removal of BFF from pituitary cultures completely restored the capacity of pituitary cultures to respond to LHRH. It was concluded that the inhibin bioassay was specific for detecting inhibin-like activity in fluids from individual follicles without interference of steroids. Within 12 h after a prostaglandin (PG) injection during the luteal phase of heifers, LH levels in serum increased 2- to 4-fold and remained at this level until the occurrence of the preovulatory gonadotropin surge. In contrast, FSH did not change before the gonadotropin surge. Inhibin bioactivity was measured in all follicles (greater than or equal to 6 mm) 0, 12, 24, 36, 48, 60, and 72 h after and in utero-ovarian venous serum 0, 24, and 36 h after PG-induced luteolysis. From 0-36 h after PG administration, inhibin-like activity increased linearly in presumed ovulatory follicles and utero-ovarian venous serum. Then, from 48-72 h after PG treatment, before the preovulatory LH surge, inhibin activity decreased in ovulatory follicles. After the surge but before ovulation, inhibin-like activity increased in ovulatory follicles. Inhibin-like activity in atretic follicles did not change after PG treatment and was lower in atretic than ovulatory follicles. Since a single hypothalamic releasing factor, LHRH, may control the secretion of LH and FSH, increased secretion of inhibin from preovulatory follicles before the preovulatory LH and FSH surges could account for the absence of a presurge rise in FSH in blood, as was observed for LH during this time in heifers. Diminished follicular production of inhibin during the gonadotropin surge could explain the preovulatory release of FSH along with LH during this time.
本研究的目的是开发一种生物测定法，用于测量未处理的牛卵泡液（BFF）样本中的抑制素生物活性，然后检测小母牛围排卵期排卵卵泡和闭锁卵泡以及子宫卵巢静脉血中抑制素生物活性的变化。使用大鼠垂体细胞培养系统对抑制素样活性进行生物测定。向垂体培养物中添加0.005至1微升未处理的（全）、未过滤的经活性炭处理的或过滤后的全BFF，可导致促性腺激素释放激素（LHRH）诱导的促卵泡素（FSH）释放呈线性抑制，但对促黄体素（LH）分泌无影响。BFF中的类固醇不会抑制FSH分泌，因为用活性炭去除BFF中的类固醇并不会消除BFF中的FSH抑制活性。添加BFF的乙醚提取物会导致FSH分泌有轻微但不平行的抑制；然而，加热这些提取物会消除大部分这种抑制活性。从垂体培养物中去除BFF可完全恢复垂体培养物对LHRH的反应能力。得出的结论是，抑制素生物测定法对于检测单个卵泡液中的抑制素样活性具有特异性，不受类固醇的干扰。在小母牛黄体期注射前列腺素（PG）后12小时内，血清中的LH水平增加2至4倍，并维持在该水平直至排卵前促性腺激素激增出现。相比之下，在促性腺激素激增之前FSH没有变化。在PG诱导黄体溶解后0、12、24、36、48、60和72小时，对所有（大于或等于6毫米）卵泡以及子宫卵巢静脉血清中的抑制素生物活性进行了测量。在PG给药后0至36小时，推测的排卵卵泡和子宫卵巢静脉血清中的抑制素样活性呈线性增加。然后，在PG处理后48至72小时，在排卵前LH激增之前，排卵卵泡中的抑制素活性下降。在激增后但排卵前，排卵卵泡中的抑制素样活性增加。PG处理后闭锁卵泡中的抑制素样活性没有变化，且闭锁卵泡中的抑制素样活性低于排卵卵泡。由于单一的下丘脑释放因子LHRH可能控制LH和FSH的分泌，排卵前卵泡在排卵前LH和FSH激增之前抑制素分泌增加可以解释血液中FSH在激增前没有升高，就像在这段时间小母牛中LH的情况一样。在促性腺激素激增期间卵泡抑制素产生减少可以解释这段时间FSH与LH一起排卵前释放的现象。
