Huggard D, Khakoo Z, Kassam G, Habibi H R
Department of Biological Sciences, University of Calgary, AB, Canada.
Can J Physiol Pharmacol. 1996 Sep;74(9):1039-46.
This study investigated the effects of testosterone and a nonaromatizable androgen, 11 beta-hydroxyandrosterone, on growth hormone gene expression in the goldfish pituitary. In the sexually immature goldfish, treatment with physiological doses of both testosterone and 11 beta-hydroxyandrosterone significantly increased the growth hormone mRNA production above basal levels. However, at supraphysiological doses, treatment with these androgens resulted in a lower level of stimulation or an inhibition of growth hormone mRNA levels. In sexually mature goldfish, testosterone treatment stimulated growth hormone mRNA levels in a dose-related fashion, with a lower level of sensitivity compared with sexually immature fish. To investigate the direct action of testosterone at the level of the pituitary, studies were performed in vitro, using isolated pituitaries obtained from both sexually immature and mature goldfish. A dose-dependent stimulation of the pituitary growth hormone mRNA level was observed in both sexually immature and mature goldfish. Overall, the present results indicate that physiological concentrations of androgens stimulate pituitary growth hormone synthesis in both sexually immature and mature goldfish. The observed stimulatory effect of testosterone occurs directly at the level of the pituitary, although it is possible that testosterone may also exert indirect effects through other neuroendocrine factors.
本研究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生长激素基因表达的影响。在性未成熟的金鱼中，用生理剂量的睾酮和11β-羟基雄甾酮处理均显著提高了生长激素mRNA的产生量，使其高于基础水平。然而，在超生理剂量下，用这些雄激素处理导致生长激素mRNA水平的刺激作用降低或受到抑制。在性成熟的金鱼中，睾酮处理以剂量相关的方式刺激生长激素mRNA水平，与性未成熟的鱼相比，敏感性较低。为了研究睾酮在垂体水平的直接作用，使用从性未成熟和成熟金鱼获得的分离垂体进行了体外研究。在性未成熟和成熟金鱼中均观察到垂体生长激素mRNA水平的剂量依赖性刺激。总体而言，目前的结果表明，生理浓度的雄激素在性未成熟和成熟金鱼中均刺激垂体生长激素的合成。观察到的睾酮刺激作用直接发生在垂体水平，尽管睾酮也可能通过其他神经内分泌因子发挥间接作用。
