Stamper D L, Licht P
Department of Integrative Biology, University of California, Berkeley 94720.
Gen Comp Endocrinol. 1994 Jan;93(1):93-102. doi: 10.1006/gcen.1994.1011.
The influence of androgen on pituitary sensitivity to gonadotropin-releasing hormone (GnRH) was investigated in juvenile female bullfrogs. Newly metamorphosed bullfrogs were treated in vivo for 7 days or their pituitaries were treated in vitro for 24 hr with 5 alpha-dihydrotestosterone (DHT). Pituitary sensitivity to GnRH was assessed by incubating glands with 100 ng/ml GnRH. The secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) was quantified by separate radioimmunoassays. Gth biosynthesis was quantified using immunoprecipitation to measure the incorporation of [35S]methionine. Prior exposure to DHT, in vitro or in vivo, significantly elevated the GnRH-induced secretion of LH and FSH. However, DHT had a differential influence on the two gonadotropins; both the basal and the GnRH-induced secretion of LH was enhanced, whereas only the GnRH-induced secretion of FSH was elevated. DHT did not significantly alter Gth biosynthesis. Treating older frogs (5 months postmetamorphic) in vivo with DHT (for 7 days) combined with a GnRH agonist (GnRHa) for 3 days enhanced the GnRH-stimulated Gth biosynthesis compared to treatment with either DHT or GnRHa alone. Therefore, while DHT may act on the pituitary to enhance gonadotropin secretion in response to GnRH, this action does not result in a concomitant increase in Gth biosynthesis. Juvenile female bullfrogs may require an increase in both GnRH and DHT in order to stimulate Gth biosynthesis.
在幼年雌性牛蛙中研究了雄激素对垂体对促性腺激素释放激素（GnRH）敏感性的影响。将刚变态的牛蛙进行7天的体内处理，或将其垂体用5α-双氢睾酮（DHT）进行24小时的体外处理。通过将腺体与100 ng/ml GnRH一起孵育来评估垂体对GnRH的敏感性。通过单独的放射免疫测定法定量黄体生成素（LH）和促卵泡激素（FSH）的分泌。使用免疫沉淀法测量[35S]甲硫氨酸的掺入量来定量促性腺激素（Gth）的生物合成。体外或体内预先暴露于DHT可显著提高GnRH诱导的LH和FSH分泌。然而，DHT对这两种促性腺激素有不同的影响；LH的基础分泌和GnRH诱导的分泌均增强，而只有GnRH诱导的FSH分泌升高。DHT并未显著改变Gth的生物合成。与单独用DHT或GnRHa处理相比，用DHT（体内处理7天）和GnRH激动剂（GnRHa）联合处理老年牛蛙（变态后5个月）3天可增强GnRH刺激的Gth生物合成。因此，虽然DHT可能作用于垂体以增强对GnRH的促性腺激素分泌，但这种作用并不会导致Gth生物合成同时增加。幼年雌性牛蛙可能需要GnRH和DHT都增加才能刺激Gth生物合成。
