Differential production and regulation of two gonadotropins (GTH I and GTH II) in teleost pituitary gonadotrophs during reproductive development.

从鲑鱼脑垂体中分离纯化出两种不同的促性腺激素(GTH I和GTH II)。化学和生物学特性表明，GTH-II是与性腺成熟和排卵有关的促性腺激素，但GTH-I是一种新的激素，其生理功能尚不清楚。免疫细胞化学表明，鲑鱼脑垂体中两种不同的促性腺激素(GTH I和GTH II)主要由两种不同的促性腺激素合成。此外，与排卵期相比，鲑鱼卵黄形成期血浆中GTH I的含量相对较高。本研究利用原位杂交组织化学方法，利用α和β亚基的cDNA探针，研究了虹鱼(*)垂体促性腺激素在生殖发育过程中促性腺激素亚单位的差异产生和调节。(1)未成熟虹鱼的GTH I和GTH IIα亚基的信使核糖核酸的表达先于GTH I和GTH II的β亚基的信使信号。(2)GTH-β亚基的mRNA在卵黄形成早期即可观察到，始终先于GTH-II，在卵黄发生期呈上升趋势，成熟前下降。(3)在性腺发育的卵黄发生后期和成熟期，GTH IIβ亚基的mRNA开始显著增加。这些结果表明，GTH I的合成早于GTH II的卵黄发生早期，并可能在卵巢的卵黄发生过程中发挥作用。然而，GTH-I和GTH-II之间的功能关系，就像哺乳动物脑下垂体中的FSH和LH一样，仍未得到解决。

Two chemically distinct gonadotropins (GTH I and GTH II) have been purified from chum salmon pituitary. Chemical and biological characterizations have revealed that GTH II is the gonadotropin concerning gonadal maturation and ovulation, however, GTH I is a new hormone and its physiological function still remains unknown. Immunocytochemistry, Lising specific antisera to beta-subunit of GTH I and GTH II, have suggested that two distinct gonadotropins (GTH I and GTH II) are synthesized mainly in two distinct gonadotrophs in salmoned pituitary. In addition, GTH I content in blood plasma is relatively high in vitellogenic phase as compared with in ovulating phase in salmoneds.This study examined differential production and regulation of gonadotropins sub-units in rainbow trout (*) pituitary gonadotrophs during reproductive development, using cDNA probes of their alpha - and beta-subunits by in situ hybridization histochemistry. (1) The mRNA of alpha -subunit of GTH I and GTH II were detected prior to any signals of beta- subunits of GTH I or GTH II in immature rainbow trouts. (2) The mRNA of beta-subunit of GTH I were observed in the early phase of vitellogenic phase, always prior to that of GTH II, and increased during vitellogenic phase and then declined before maturation. (3) The mRNA of beta-subunit of GTH II began to increase extremely during post vitellogenic and maturating phases of gonadal development. These results suggest that GTH I-synthesis occurs from early vitellogenic phase prior to that of GTH II, and may play functional role during vitellogenesis in the ovary. However, functional relationship between GTH I and GTH II, just like FSH and LH in mammalian pituitary, still remains unsolved.