Krummen L A, Morelos B S, Bhasin S
Department of Medicine, Harbor-UCLA Medical Center, Torrance 90502.
Endocrinology. 1990 Sep;127(3):1097-104. doi: 10.1210/endo-127-3-1097.
In vivo and in vitro evidence indicates that FSH is a primary regulator of testicular inhibin production. However, recent reports suggest that LH may also promote inhibin secretion in vivo. To investigate whether LH regulates inhibin subunit messenger RNA (mRNA) expression as well, we examined the effects of hypophysectomy and LH replacement on the testicular content of inhibin alpha and beta-B subunit mRNAs in sexually immature and adult rats. Twenty- and 60-day-old intact and hypophysectomized rats received saline or 0.25, 2.5, 25.0, or 250 micrograms ovine LH/100 g body wt sc, twice daily for 7 days beginning on the day after hypophysectomy (n = 5/group in three separate experiments). The inhibin subunit mRNA content of each testis was measured for statistical analysis by dot-blot hybridization, and experimental results were confirmed by northern analysis of poly(A) RNA from each sample. In immature animals, the testicular content of both inhibin subunit mRNAs was decreased after hypophysectomy; inhibin alpha and beta-B mRNA levels were decreased to 6.9 +/- 0.9% and 31.7 +/- 2.7% of intact control values, respectively. In adult animals, hypophysectomy resulted in a more modest decrease in inhibin alpha subunit mRNA per testis (44.9 +/- 3.1% of controls) but had no effect on beta-B subunit mRNA. Replacement of LH to immature hypophysectomized animals did not alter levels of mRNA for either inhibin subunit. However, in adults LH restored testicular inhibin alpha subunit mRNA content in testes of hypophysectomized animals to levels seen in intact, saline-treated control animals. LH replacement also slightly but consistently decreased testicular beta-B subunit mRNA content compared to levels seen in hypophysectomized, saline-treated rats. These results indicate that although the response of inhibin subunit mRNAs to pituitary input decreases as a function of sexual maturation, LH may play an important role in regulation of inhibin subunit mRNA expression in adult but not immature testes. The mechanism(s) of LH action on testicular inhibin subunit gene expression is currently unknown, but may involve either direct actions of LH on Leydig cell inhibin subunit mRNAs or indirect actions of interstitial cell factors on Sertoli cell inhibin subunit gene expression.
体内和体外证据表明，促卵泡激素（FSH）是睾丸抑制素产生的主要调节因子。然而，最近的报告表明，促黄体生成素（LH）在体内也可能促进抑制素的分泌。为了研究LH是否也调节抑制素亚基信使核糖核酸（mRNA）的表达，我们检测了垂体切除和LH替代对性未成熟和成年大鼠睾丸中抑制素α和β - B亚基mRNA含量的影响。20日龄和60日龄的完整和垂体切除大鼠，在垂体切除后第二天开始，每天皮下注射生理盐水或0.25、2.5、25.0或250微克羊LH/100克体重，每日两次，共7天（在三个独立实验中每组n = 5）。通过斑点杂交对每个睾丸的抑制素亚基mRNA含量进行测量以进行统计分析，实验结果通过对每个样本的聚腺苷酸（poly(A)）RNA进行Northern分析得到证实。在未成熟动物中，垂体切除后两个抑制素亚基mRNA的睾丸含量均降低；抑制素α和β - B mRNA水平分别降至完整对照值的6.9±0.9%和31.7±2.7%。在成年动物中，垂体切除导致每个睾丸中抑制素α亚基mRNA的降低更为适度（为对照的44.9±3.1%），但对β - B亚基mRNA没有影响。对未成熟垂体切除动物补充LH并没有改变任何一种抑制素亚基的mRNA水平。然而，在成年动物中，LH将垂体切除动物睾丸中的抑制素α亚基mRNA含量恢复到完整、生理盐水处理对照动物的水平。与垂体切除、生理盐水处理的大鼠相比，LH替代也使睾丸β - B亚基mRNA含量略有但持续降低。这些结果表明，尽管抑制素亚基mRNA对垂体输入的反应随性成熟而降低，但LH可能在成年而非未成熟睾丸中抑制素亚基mRNA表达的调节中起重要作用。目前尚不清楚LH对睾丸抑制素亚基基因表达的作用机制，但可能涉及LH对睾丸间质细胞抑制素亚基mRNA的直接作用或间质细胞因子对支持细胞抑制素亚基基因表达的间接作用。
