Sreenivasulu G, Senthilkumaran B. New evidences for the involvement of 20beta-hydroxysteroid dehydrogenase in final oocyte maturation of air-breathing catfish.
Gen Comp Endocrinol 2009;
163:259-69. [PMID:
19401204 DOI:
10.1016/j.ygcen.2009.04.022]
[Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Revised: 04/15/2009] [Accepted: 04/20/2009] [Indexed: 11/26/2022]
Abstract
20beta-hydroxysteroid dehydrogenase (20beta-HSD) synthesizes 17alpha,20beta-dihdroxy-4-pregnen-3-one, the steroid required for resumption of prophase-I arrested oocytes in teleosts. Though 20beta-HSD cDNAs have been cloned from few fish species, its role in final oocyte maturation (FOM) is still questionable. To study the role of 20beta-HSD in FOM more explicitly, we cloned and characterized 20beta-HSD from ovary of air-breathing catfish, Clarias gariepinus. Interestingly, Escherichia coli expressed recombinant proteins, both full-length and an N-terminal truncated proteins catalyzed the reduction of steroids and xenobiotics, however there was significant difference between them. Semi-quantitative RT-PCR and Western blots demonstrated the presence of 20beta-HSD transcript and protein in various tissues with relatively higher level in gonads, gill, kidney and brain. A positive correlation of 20beta-HSD expression was observed in different phases of ovarian cycles. Immunocytochemical/immunofluoroscence analysis with specific antibody identified presence of 20beta-HSD in follicular layer of ovary. Real-time RT-PCR and Western blotting showed an induction of 20beta-HSD expression during human chorionic gonadotropin (hCG)-induced oocyte maturation, in vitro and in vivo. Concomitantly, a rise in 20beta-HSD enzyme activity was also noticed. Specific inhibitors of carbonyl reductase inhibited not only recombinant protein catalytic activity but also hCG-induced oocyte maturation in a dose-dependent manner as evidenced by blocking of germinal vesicle break down. These results together provide new evidences for the involvement of 20beta-HSD in the FOM/meiotic maturation.
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