诱导大鳍鱯和长吻鮠排卵过程中血清GTH水平的变化

CHANGES IN SERUM GTH LEVELS DURING THE INDUCED OVULATION OF THE LARGE FIN LONG BARBEL CATFISH, MYSTUS MACROPTERUS AND LEIOCASSIS LONGIROSTRIS

繁殖期从嘉陵江收集性成熟的大鳍■ 和长吻 野生亲鱼，用Ｌｉｎｐｅ方法（即ＬＨＲＨ－Ａ加多巴胺Ｄ２受体拮抗剂地欧酮）或传统的ＬＨＲＨ—Ａ加脑垂体的方法进行催产，定时取血样，用放射免疫方法测定催产过程中血清ＧＴＨ水平的变化，进一步证实鲇形目鱼类ＧＴＨ的分泌受到下丘脑分泌的促性腺激素释放激素ＧｎＲＨ和多巴胺的双重调节；排卵和产卵也是以血清ＧＴＨ的急剧升高为先导的，而最终能否排卵还有赖于血清ＧＴＨ峰是否超过“排卵阈值”。尽管催产后的大鳍 和长吻 雄鱼血清ＧＴＨ水平也有一个高峰出现，但血清ＧＴＨ水平升高幅度都大大低于雌鱼，这种现象在硬骨鱼类可能具有普遍性。

Mystus macropterus (Bleeker) and Leiocassis longirostris Guntherwere collected from the Jialing River, a tributary of the Yangtze River, during their spawning season. The homologous radioimmunoassay (RIA) for African catfish, Clarias gariepinus, gonadotropin was used to determine the serum GTH levels of these two fishes during the induced ovulation by injecting luteinizing hormone-releasing hormone analogue (LHRH-A) plus domperidone (DOM), D2 receptor antagonist of dopamine (DA) for M. macropterus and by injecting LHRH-A plus silver carp pituitary suspension (SCPS) for L. longirostris. Like most teleosts, the gonadotropin release of these two fishes was under the dual regulation of gonadotropin-releasing-hormone (GnRH) and DA from the hypothalamus. In M. macropterus, LHRH-A alone stimulated GTH secretion, and DOM potentiated this effect of LHRH-A. Whereas DOM alone had no effect on basal GTH secretion of the fish. A preovulatory GTH surge was found prior to the ovulation of these two fishes. Ovulation cannot be successfully induced unless the preovulatory serum GTH peak could surpass a threshold. The induced serum GTH peak for males were much lower than that for females, although male’s serum GTH level also elevated rapidly before spermiation. Similar cases were found in some other teleosts, both in natural and induced spawning condition.