外源激素对南方鲶血清促性腺激素水平的影响

Effects of Exogenous Hormones on the Level of Serum Gonadotropin in Southern Catfish (Silurus meridionalis)

南方鲶1龄幼鱼促性腺激素(GTH)分泌调节研究表明:南方鲶幼鱼GTH的释放受到促性腺激素释放激素(GnRH)和多巴胺(DA)的双重调控,但DA不能抑制基础的GTH释放,而只能抑制GnRH刺激的GTH释放,DA对GTH的释放抑制作用是间接通过GnRH实现的.这与研究过的鲤科鱼类不同,而与研究过的其它鲶形目鱼类相似.注射人绒毛膜促性腺激素(hCG)后南方鲶血清GTH水平上升,hCG促使血液GTH水平升高可能与hCG与非洲鲶促性腺激素抗体具有一定的交叉免疫反应有关.hCG与促黄体释放激素类似物(LHRH A)结合注射后血清GTH水平也显著高于单独注射hCG或LHRH A后的血清GTH水平,这种升高可能来源于外源GTH(hCG)和LHRH A刺激脑垂体分泌的内源GTH.

Like most other teleosts, the GTH release of the oneyearold Southern catfish is under the dual regulation of gonadotropinreleasing hormone(GnRH) and dopamine(DA) from the hypothalamus. LHRHA alone stimulated GTH secretion, and domperidone (DOM), D2 receptor antagonist of DA, potentiated this effect, although DOM alone had no effect on basal GTH secretion, which indicated that DA does not affect the GTH release directly, but modulates the effect of GnRH. This kind of inhibitory mechanism may be popular among catfishes,as has been proved in some other catfishes that have been studied. It is to some extent different from the results got from the Cyprinids, in which DA inhibit basal as well as GnRH stimulated GTH release from pituitary.The serum GTH levels increased after injection of hCG in oneyearold Southern catfishes. The increase may be attributed to the immune crossreaction between hCG and cfGTH. Much higher GTH levels were detected after a combined injection of hCG and LHRHA. The high serum GTH levels detected may come from both exogenous hCG and endogenous GTH from pituitary stimulated by LHRHA.