Peyon P, Baloche S, Burzawa-Gerard E
Laboratoire de Physiologie Generale et Comparée, CNRS, Paris, France.
Gen Comp Endocrinol. 1996 May;102(2):263-73. doi: 10.1006/gcen.1996.0068.
Previous in vivo experiments have indicated a potentiating role of growth hormone (GH) during experimentally induced vitellogenesis by 17-beta-estradiol (E2) in the female silver eel (Anguilla anguilla L.). To investigate whether GH has direct hepatic actions, the effects of hypophysial-purified and recombinant QH on vitellogenin (Vg) synthesis in response to E2 were tested on primary cultures of hepatocytes. Hepatocytes were prepared from control or E2-primed eels. Addition of E2 alone into the culture medium induced both Vg synthesis and secretion in a dose- and time-related fashion. Bovine growth hormone (bGH) alone had no effect on the induction of Vg synthesis or secretion. Bovine GH enhanced the in vitro effects of F2 on both Vg synthesis and secretion, an effect attenuated by an in vivo E2 priming which was dose-dependent with an ED(50) of 5 ng/ml. To investigate the specificity of GH action, purified eel and salmon GH and salmon, trout, and tilapia prolactins (PRL), as well as recombinant trout and tilapia GH, were tested, and the responses were compared to bGH. Purified salmon and homologous eel GH potentiated the vitellogenic response to F2. Recombinant GH were highly efficacious, excluding the presence of active contaminants in the potentiating effect of GH preparations. The potentiating effect of recombinant trout GH on the vitellogenic response was reduced at high doses (above 20 ng/ml), suggesting a down-regulation of GH binding sites by GH itself. Salmon PRL has minimal activity, but not trout and tilapia PRL, indicating that PRL is not an important potentiating factor on Vg synthesis in our model. It is concluded that GH acts directly on the liver to potentiate E2 induction of eel hepatic Vg synthesis. The potentiating effect of GH appears to be time- and dose-dependent and modulated as a function of hormonal status (E2 priming) of the eel.
先前的体内实验表明，在实验诱导雌性欧洲鳗鲡（Anguilla anguilla L.）卵黄生成过程中，生长激素（GH）具有增强作用，该过程由17-β-雌二醇（E2）诱导。为了研究GH是否具有直接的肝脏作用，在原代肝细胞培养物上测试了垂体纯化的GH和重组GH对E2诱导的卵黄蛋白原（Vg）合成的影响。肝细胞取自对照鳗鲡或经E2预处理的鳗鲡。单独向培养基中添加E2以剂量和时间相关的方式诱导Vg的合成和分泌。单独的牛生长激素（bGH）对Vg合成或分泌的诱导没有影响。牛GH增强了E2对Vg合成和分泌的体外作用，体内E2预处理可减弱这种作用，且这种减弱呈剂量依赖性，半数有效剂量（ED50）为5 ng/ml。为了研究GH作用的特异性，测试了纯化的鳗鲡和鲑鱼GH以及鲑鱼、鳟鱼和罗非鱼的催乳素（PRL），以及重组鳟鱼和罗非鱼GH，并将反应与bGH进行比较。纯化的鲑鱼和同源鳗鲡GH增强了对E2的卵黄生成反应。重组GH非常有效，排除了GH制剂增强作用中存在活性污染物的可能性。高剂量（高于20 ng/ml）时，重组鳟鱼GH对卵黄生成反应的增强作用降低，表明GH自身对GH结合位点有下调作用。鲑鱼PRL活性最小，但鳟鱼和罗非鱼PRL并非如此，这表明在我们的模型中PRL不是Vg合成的重要增强因子。得出的结论是，GH直接作用于肝脏，增强E2对鳗鲡肝脏Vg合成的诱导作用。GH的增强作用似乎具有时间和剂量依赖性，并根据鳗鲡的激素状态（E2预处理）进行调节。
