Huggard D, Khakoo Z, Kassam G, Mahmoud S S, Habibi H R
Department of Biological Sciences, University of Calgary, Alberta, Canada.
Biol Reprod. 1996 Jun;54(6):1184-91. doi: 10.1095/biolreprod54.6.1184.
In this study, we investigated the effects of testosterone and a nonaromatizable androgen, 11 beta-hydroxyandrosterone, on maturational gonadotropin (GtH-II) subunit gene expression in the goldfish pituitary. While testosterone treatment at physiological doses resulted in stimulation of GtH-II-alpha and -beta subunit mRNA production, time-course and dose-response studies performed on sexually immature goldfish of mixed sex, using a wider dose range exceeding physiological levels, demonstrated a biphasic response to in vivo androgen treatment. Time-related treatment with testosterone and 11 beta-hydroxyandrosterone (20 micrograms/fish) resulted in an initial inhibition of GtH-II subunit mRNA production (12-24 h) followed by stimulation at 72-96 h. In dose-response studies, treatment for 24 h with testosterone resulted in a significant stimulation at the low physiological doses of 0.2 and 2 micrograms/fish. At the supraphysiological level of 20 micrograms/fish, testosterone treatment resulted in no stimulation or in decreased GtH-II subunit mRNA levels compared to the control values. Similarly, treatment with 11 beta-hydroxyandrosterone resulted in a significant stimulation of GtH-II subunit mRNA levels at low physiological concentrations (0.2 microgram/ fish) and an inhibition, or no stimulation, at higher concentrations (2-20 micrograms/fish). In sexually mature goldfish of mixed sex, the biphasic effect of testosterone was not observed in vivo, and treatment with this steroid resulted in stimulation of GtH-II subunit mRNA production in a dose-related manner. To investigate the direct action of testosterone, studies were carried out using isolated goldfish pituitary fragments from goldfish of mixed sex in vitro. Treatment with testosterone at various concentrations was found to stimulate GtH-II subunit mRNA production in pituitary glands obtained from both sexually immature and sexually mature goldfish. Overall, the present study demonstrates a stimulatory effect of testosterone on GtH-II subunit mRNA levels in goldfish. The observed stimulation of basal GtH-II subunit mRNA production by testosterone occurs, in part, through a direct action at the level of the pituitary in both sexually immature and mature goldfish.
在本研究中，我们调查了睾酮和一种不可芳香化的雄激素——11β-羟基雄甾酮对金鱼垂体中促性腺激素（GtH-II）亚基成熟基因表达的影响。虽然生理剂量的睾酮处理会刺激GtH-II-α和-β亚基mRNA的产生，但对混合性别的性未成熟金鱼进行的时程和剂量反应研究，使用了超过生理水平的更宽剂量范围，结果显示对体内雄激素处理有双相反应。用睾酮和11β-羟基雄甾酮（20微克/鱼）进行与时间相关的处理，导致GtH-II亚基mRNA产生最初受到抑制（12 - 24小时），随后在72 - 96小时受到刺激。在剂量反应研究中，用睾酮处理24小时，在0.2和2微克/鱼的低生理剂量下会导致显著刺激。在20微克/鱼的超生理水平下，与对照值相比，睾酮处理没有刺激作用或导致GtH-II亚基mRNA水平降低。同样，用11β-羟基雄甾酮处理，在低生理浓度（0.2微克/鱼）下会导致GtH-II亚基mRNA水平显著刺激，而在较高浓度（2 - 20微克/鱼）下则会抑制或没有刺激作用。在混合性别的性成熟金鱼中，未观察到睾酮的双相作用，用这种类固醇处理会以剂量相关的方式刺激GtH-II亚基mRNA的产生。为了研究睾酮的直接作用，使用来自混合性别的金鱼的离体金鱼垂体片段进行了体外研究。发现用不同浓度的睾酮处理会刺激从性未成熟和性成熟金鱼获得的垂体中GtH-II亚基mRNA的产生。总体而言，本研究证明了睾酮对金鱼GtH-II亚基mRNA水平有刺激作用。观察到的睾酮对基础GtH-II亚基mRNA产生的刺激作用，部分是通过在性未成熟和成熟金鱼垂体水平的直接作用实现的。
