Nagamine N, Nambo Y, Nagata S, Nagaoka K, Tsunoda N, Taniyama H, Tanaka Y, Tohei A, Watanabe G, Taya K
a Laboratory of Veterinary Physiology, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
Biol Reprod. 1998 Dec;59(6):1392-8. doi: 10.1095/biolreprod59.6.1392.
To determine the source of circulating inhibin and estradiol-17beta during the estrous cycle in mares, the cellular localization of the inhibin alpha, betaA, and betaB subunits and aromatase in the ovary was determined by immunohistochemistry. Concentrations of immunoreactive (ir-) inhibin, estradiol-17beta, progesterone, LH, and FSH in peripheral blood were also measured during the estrous cycle in mares. Immunohistochemically, inhibin alpha subunits were localized in the granulosa cells of small and large follicles and in the theca interna cells of large follicles, whereas inhibin betaA and betaB subunits were localized in the granulosa cells and in the theca interna cells of large follicles. On the other hand, aromatase was restricted to only the granulosa cells of large follicles. Plasma ir-inhibin concentrations began to increase 9 days before ovulation; they remained high until 2 days before ovulation, after which they decreased when the LH surge was initiated. Thereafter, a further sharp rise in circulating ir-inhibin concentrations occurred during the process of ovulation, followed by a second abrupt decline. After the decline, plasma concentrations of ir-inhibin remained low during the luteal phase. Plasma estradiol-17beta concentrations followed a profile similar to that of ir-inhibin, except during ovulation, and these two hormones were positively correlated throughout the estrous cycle. Plasma FSH concentrations were inversely related to ir-inhibin and estradiol-17beta. These findings suggest that the dimeric inhibin is mainly secreted by the granulosa cells and the theca cells of large follicles; granulosa cells of small follicles may secrete inhibin alpha subunit, and estradiol-17beta is secreted by the granulosa cells of only large follicles in mares.
为确定母马发情周期中循环抑制素和雌二醇-17β的来源，通过免疫组织化学方法确定了卵巢中抑制素α、βA和βB亚基以及芳香化酶的细胞定位。同时还测定了母马发情周期中外周血中免疫反应性（ir-）抑制素、雌二醇-17β、孕酮、促黄体生成素（LH）和促卵泡素（FSH）的浓度。免疫组织化学结果显示，抑制素α亚基定位于小卵泡和大卵泡的颗粒细胞以及大卵泡的内膜细胞，而抑制素βA和βB亚基定位于大卵泡的颗粒细胞和内膜细胞。另一方面，芳香化酶仅局限于大卵泡的颗粒细胞。血浆ir-抑制素浓度在排卵前9天开始升高，排卵前2天一直保持在较高水平，之后随着LH峰的开始而下降。此后，在排卵过程中循环ir-抑制素浓度进一步急剧上升，随后再次突然下降。下降之后，黄体期血浆ir-抑制素浓度一直保持在较低水平。血浆雌二醇-17β浓度呈现出与ir-抑制素相似的变化趋势，排卵期间除外，并且在整个发情周期中这两种激素呈正相关。血浆FSH浓度与ir-抑制素和雌二醇-17β呈负相关。这些发现表明，二聚体抑制素主要由大卵泡的颗粒细胞和内膜细胞分泌；小卵泡的颗粒细胞可能分泌抑制素α亚基，而雌二醇-17β仅由母马的大卵泡颗粒细胞分泌。
