Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Abstract

Plasma estradiol-17β (E2), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and 17α,20β,21-tri-hydroxy-4-pregnen-3-one (20β-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20β-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E2 and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20β-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E2 and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20β-S and oocyte GVBD by white perch follices. DHP and 20β-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20β-S in the control of FOM in white perch and white bass.

A Receptor for the Oocyte Maturation-Inducing Hormone 17α,20β,21-Trihydroxy- 4-Pregnen-3-One on Ovarian Membranes of Striped Bass1

“…Binding by DHP to ovarian membranes was relatively low and did not fulfill any of the criteria for a hormone receptor. Together with the findings of previous studies of in vivo and in vitro FOM in striped bass and related species (genus Morone) [15,16,27], these results indicate that 203-S is the MIH in striped bass.…”

The Catecholestrogen, 2-Hydroxyestradiol-17beta, Acts as a G Protein-Coupled Estrogen Receptor 1 (GPER/GPR30) Antagonist to Promote the Resumption of Meiosis in Zebrafish Oocytes1

“…However, substantial amounts of E 2 , aromatase activity and cyp19A mRNA expression were still present in zebrafish follicles during the early stages of OM, similar to the findings in rainbow trout [46]. Moreover, transient increases in E 2 production in Atlantic croaker ovaries in vitro and circulating E 2 levels in white perch and striped bass have also been observed during the initial stages of gonadotropin induction of OM [47][48][49]. These results are consistent with role of E 2 in the early stages of OM, preventing precocious resumption of meiosis [22,24,50].…”

Role of G protein-coupled estrogen receptor 1, GPER, in inhibition of oocyte maturation by endogenous estrogens in zebrafish

“…In support of this increased production of E2 and T was observed by croaker ovarian follicles in response to gonadotropin treatment at the onset of oocyte maturation (Trant and Thomas, 1989). In addition, peaks in plasma E2 and T concentrations have been observed after gonadotropin treatment in white perch and striped bass that were at the germinal vesicle migration stage of oocyte maturation followed by declines in circulating E2 levels in later maturation stages (King et al, 1994; King et al, 1995). Similar increases in plasma E2 levels were observed in wild-caught white perch white bass, gilthead seabream and sea bass around the time of spawning (Kadmon et al, 1985; Prat et al, 1990; Berlinsky et al, 1995; Jackson and Sullivan, 1995).…”