Sohn Y C, Kobayashi M, Aida K
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, 113-8657, Tokyo, Japan.
Comp Biochem Physiol B Biochem Mol Biol. 2001 Jun;129(2-3):419-26. doi: 10.1016/s1096-4959(01)00342-6.
Sex steroids differentially regulate gonadotropin (GTH) beta subunits (FSHbeta and LHbeta) gene expression in the pituitary of goldfish: a strong in vivo inhibitory effect on FSHbeta mRNA production, but a weak stimulatory effect on LHbeta in sexually immature and recrudescent fish. In the present study, to examine a direct effect of testosterone (T) and gonadotropin-releasing hormone (GnRH) on the mRNA levels of FSHbeta and LHbeta subunits in the pituitary, in vitro experiments were performed using dispersed pituitary cells of sexually immature, recrudescent, mature and regressed goldfish. T treatment in vitro did not significantly decrease FSHbeta mRNA levels, but increased that of LHbeta only in the cells of immature fish. Salmon-type GnRH increased FSHbeta mRNA levels in cells of mature fish, but decreased the levels in cells of sexually regressed fish. From these results, it was suggested that: (1) in vivo effect of sex steroids on gene expression of GTH beta subunits is not always exerted on the pituitary; and (2) the different responses of GTH beta subunits by sex steroids between in vivo and in vitro are partly due to a complex pathway through hypothalamic factors, such as GnRH, in the case of in vivo.
性类固醇对金鱼垂体中促性腺激素（GTH）β亚基（FSHβ和LHβ）基因表达有不同调节作用：对性未成熟和性腺再发育的金鱼，对FSHβ mRNA产生有强烈的体内抑制作用，但对LHβ有微弱的刺激作用。在本研究中，为检测睾酮（T）和促性腺激素释放激素（GnRH）对垂体中FSHβ和LHβ亚基mRNA水平的直接影响，使用性未成熟、性腺再发育、成熟和性腺退化金鱼的分散垂体细胞进行了体外实验。体外T处理并未显著降低FSHβ mRNA水平，但仅在未成熟鱼的细胞中增加了LHβ的mRNA水平。鲑鱼型GnRH增加了成熟鱼细胞中FSHβ mRNA水平，但降低了性腺退化鱼细胞中的水平。从这些结果表明：（1）性类固醇对GTHβ亚基基因表达的体内作用并不总是作用于垂体；（2）性类固醇在体内和体外对GTHβ亚基的不同反应部分是由于在体内情况下通过下丘脑因子（如GnRH）的复杂途径。
