The duality of teleost gonadotropins

Abstract

The duality of salmon gonadotropins has been proved by biochemical, biological, and immunological characterization of two chemically distinc gonadotropins. GTH I and GTH II were equipotent in stimulating estradiol production, whereas GTH II appears to be more potent in stimulating maturational steroid synthesis. The ratio of plasma levels and pituitary contents of GTHs and the secretory control by a GnRH suggest that GTH I is the predominant GTH during vitellogenesis and early stages of spermatogenesis in salmonids, whereas GTH II is predominant at the time of spermiation and ovulation. GTH I and GTH II are found in distinctly separate cells. In trout, GTH I is expressed first in ontogeny, whereas GTH II cells appear coincident with the onset of spermatogenesis and vitellogenesis, and increase dramatically at the time of final reproductive maturation. Comparison of the amino acid sequences of polypeptides and the base sequences of cDNA revealed that salmon GTH I β is more similar to bovine FSHβ than bovine LHβ and salmon GTH II β shows higher homology to bovine LHβ than to bovine FSHβ. The existence of two pituitary gonadotropins in teleosts as well as tetrapods suggests that the divergence of the GTH gene took place earlier than the time of divergence of teleosts from the main line of evolution leading to tetrapods.

Molecular characterization of Chinese sturgeon gonadotropins and cellular distribution in pituitaries of mature and immature individuals

“…Our results suggested that the expression pattern of Chinese sturgeon LH␤ might be similar to that observed in salmonids. In teleosts, the duality of FSH␤ and LH␤ was first revealed by Kawauchi et al (1989) and has been demonstrated in a number of species (Koide et al, 1993;Okada et al, 1994;Hassin et al, 1995;Elizur et al, 1996;García-Hernández et al, 1997;Kagawa et al, 1998;Calman et al, 2001;Mateos et al, 2003;Li et al, 2005;Cerdà et al, 2008). However, it is still unclear whether the FSH␤ and LH␤ are synthesized in the same cells as it occurs in tetrapods (Saito et al, 2002).…”

Visão geral sobre reprodução de peixes teleósteos: da anatomia à sinalização molecular

“…Os hormônios gonadotróficos FSH e LH regulam a gametogênese em vertebrados por meio da estimulação da síntese de esteróides sexuais (Kawauchi et al, 1989). O padrão de liberação das gonadotrofinas em peixes sugere que o FSH tem um papel fundamental na regulação do crescimento de folículos vitelogênicos por meio da estimulação da biossíntese do estradiol-17b (E2) pelos folículos ovarianos.…”

Periovulatory changes in catfish ovarian oestradiol-17beta, oestrogen-2-hydroxylase and catechol-O-methyltransferase during GnRH analogue-induced ovulation and in vitro induction of oocyte maturation by catecholoestrogens

“…The vitellogenic phase is initiated and maintained by one of the gonadotrophins (gonadotrophin-I (GTH-I) or follicle-stimulating hormone (FSH)) in the two gonadotrophin model species (Kawauchi et al 1989, Yoshikuni & Nagahama 1991, Swanson & Dittman 1997 through the mediation of ovarian oestrogens, principally oestradiol-17 (OE 2 ). Oocyte maturational and ovulatory events are initiated by the other gonadotrophin (gonadotrophin-II (GTH-II) or luteinizing hormone (LH)) through the mediation of a maturation-inducing hormone or substance (MIH or MIS), the most common being an ovarian progesterone derivative, 17 , as in many salmonids, cyprinids and silurids, or 17 ,20 ,20 , as in sciaenid fish (Goetz 1983, Nagahama 1987, Scott & Canario 1987, Thomas 1994.…”