Abstract
BackgroundThe gonadotropins (GtHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are produced in the pituitary gland and regulates gametogenesis through production of gonadal steroids. However, respective roles of two GtHs in the teleosts are still incompletely characterized due to technical difficulties in the purification of native GtHs.MethodsNative FSH and LH were purified from the pituitaries of adult chub mackerel, Scomber japonicus by anion-exchange chromatography and immunoblotting using specific antisera. The steroidogenic potency of the intact chub mackerel FSH (cmFSH) and LH (cmLH) were evaluated in mid- and late-vitellogenic stage follicles by measuring the level of gonadal steroids, estradiol-17beta (Ε2) and 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P). In addition, we evaluated the maturation-inducing potency of the GtHs on same stage follicles.ResultsBoth cmFSH and cmLH significantly stimulated E2 production in mid-vitellogenic stage follicles. In contrast, only LH significantly stimulated the production of 17,20beta-P in late-vitellogenic stage follicles. Similarly, cmLH induced final oocyte maturation (FOM) in late-vitellogenic stage follicles.ConclusionsPresent results indicate that both FSH and LH may regulate vitellogenic processes, whereas only LH initiates FOM in chub mackerel.
Highlights
The gonadotropins (GtHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are produced in the pituitary gland and regulates gametogenesis through production of gonadal steroids
In vitro and in vivo experiments using purified GtHs have shown that FSH is involved in the vitellogenic growth of oocytes by stimulating estradiol-17β (Ε2) production, whereas LH mediates final oocyte maturation (FOM) through the production of the maturation-inducing steroid (MIS), 17,20β-dihydroxy-4pregnen-3-one (17,20β-P) [8,9]
Purification and biochemical properties of chub mackerel FSH (cmFSH) and cmLH Ethanol-extracted glycoproteins from chub mackerel pituitaries were separated by DEAE anion-exchange chromatography (Figure 1 Upper)
Summary
The gonadotropins (GtHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are produced in the pituitary gland and regulates gametogenesis through production of gonadal steroids. Pituitary gonadotropins (GtHs), follicle-stimulating hormone (FSH), and luteinizing hormone (LH), are key central signaling molecules on the BPG axis. GtHs regulate different stages of ovarian development by stimulating gonadal steroid production in the somatic cells surrounding the germ cells [1,2]. Specific roles for teleost GtHs have been revealed mainly in salmonids, which exhibit synchronous or group-synchronous ovarian development and spawn single batch of eggs. These features enable an easy correlation between changes in endocrine hormones and ovarian development. Regulating the synthesis and secretion of pituitary GtH is likely more complicated during the spawning cycle
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