GnRH_A和紫萁抑制大黄鱼性腺早熟的机制

应用脑垂体组织生理学和免疫组织化学方法，对GnRH-A和紫萁抑制大黄鱼性早熟的作用机制进行了研究。结果表明，性早熟大黄鱼脑垂体许多促性腺激素分泌细胞的胞质出现空泡，提示性早熟的原因可能是由于GtH细胞提早进入分泌活动所致。长期服用促性腺激素释放激素类似物的养殖大黄鱼（没有性早熟），它的脑垂体GtH细胞对GnRH抗独特型发生弱的免疫阳性反应，而对照组性早熟鱼仍出现强的反应，表明实验组大黄鱼脑垂体GtH细胞对GnRH-A的应答能力下降，出现脱敏效应，这可能与GnRH-A抑制大黄鱼性早熟有关。养殖大黄鱼长期服用紫萁，它的脑垂体GtH细胞膜上GnRH受体则没有出现脱敏现象，提示紫萁抑制大黄鱼性早熟的机制不同于GnRH类似物，确切机制有待进一步研究。

The mechanism of inhibitory gonadal precocity of GnRH-A and Ziqi in cultured Pseudosciaena crocea

The mechanism of inhibitory gonadal precocity of GnRH A and Zipi in cultured large yellow croaker was studied using pituitary histophysiological methods.The present results indicate that it occurred vacuole in the cytoplasms of many gonadotropic cells in the pituitary of gonadal precocity,which shows that the cause of gonadal precocity may be due to entering the secretory activity of GtH cells in pituitary.The GtH cells of the cultured large yellow croaker,which had been fed with food containing GnRH A,showed a weak immunopositive reaction to GnRH anti idiotypic antibodies,while those of the gonadal precocity in the control group showed a strong immunopositive reaction.These results indicate that responsive capability of GtH cells in the experimental group to GnRH A are weakened,and desensitization effect occurred.It may relate with GnRH A inhibitory gonadal precocity of large yellow croaker.GnRH receptor on the membrane of GtH cell of the cultured fish,which had been fed with food containing Ziqi,did not showed desensitization phenomenon,which indicates the mechanism of inhibitory gonadal precocity of Ziqi differs from GnRH analogues.However,the definitive mechanism still needs further study.