title: Expression and immunolocalization of 20β-hydroxysteroid dehydrogenase during testicular cycle and after hCG induction, in vivo in the catfish, Clarias gariepinus.
abstract: The maturation inducing hormone, 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DP) is required for the meiotic maturation and is produced from the precursor 17α-hydroxyprogesterone by the enzyme 20β-hydroxysteroid dehydrogenase (20β-HSD) in several teleosts. Central role of 20β-HSD in ovarian cycle and final oocyte maturation is well studied when compared to spermatogenesis. In the present study, we investigated the localization and expression of 20β-HSD in testicular cycle and gonadotropin induced sperm maturation. During testicular ontogeny, 20β-HSD expression was detectable at 50 and 100 days post-hatch (dph), while the expression was high at 150 dph. In testicular cycle, highest levels of mRNA and protein of 20β-HSD were observed during spawning phase. Intraperitoneal injection of human chorionic gonadotropin (hCG) to prespawning catfish elevated both 20β-HSD transcripts and protein levels when compared to saline treated controls in a time-dependent manner. Serum 17α,20β-DP levels, measured during different phases of testicular cycle as well as following the treatment of hCG, showed a positive correlation with the expression of 20β-HSD. Immunolocalization revealed the presence of 20β-HSD protein predominantly in interstitial cells and spermatogonia/spermatocytes while 20β-HSD was undetectable in haploid cells (spermatids/sperm). These results together with high expression during spawning phase of testicular cycle and after hCG treatment in the prespawning catfish suggests a pivotal role for 20β-HSD during testicular recrudescence leading to sperm maturation. Further studies using various fish models on testicular 20β-HSD may provide interesting details to understand its importance in teleostean spermatogenesis.
authors.affiliation: Department of Animal Sciences, School of Life Sciences-Centre for Advanced Studies, University of Hyderabad, PO Central University, Hyderabad, Andhra Pradesh 500 046, India.
authors.forename: G
authors.initials: G
authors.lastname: Sreenivasulu
authors.forename: B
authors.initials: B
authors.lastname: Senthilkumaran
authors.forename: P
authors.initials: P
authors.lastname: Sridevi
authors.forename: A
authors.initials: A
authors.lastname: Rajakumar
authors.forename: M K
authors.initials: MK
authors.lastname: Rasheeda
mesh_terms: D000818:Animals; D002397:Catfishes / Q000378:metabolism*; D006063:Chorionic Gonadotropin / Q000008:administration & dosage / Q000494:pharmacology*; D003349:Cortisone Reductase / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D006908:Hydroxyprogesterones / Q000097:blood; D007274:Injections, Intraperitoneal; D007985:Leydig Cells / Q000201:enzymology; D008297:Male; D012621:Seasons; D013090:Spermatocytes / Q000201:enzymology; D013091:Spermatogenesis / Q000187:drug effects* / Q000502:physiology*; D013737:Testis / Q000166:cytology / Q000201:enzymology*
chemical_list: D006063:Chorionic Gonadotropin; D018076:DNA, Complementary; D006908:Hydroxyprogesterones; C007433:17,20-dihydroxy-4-pregnen-3-one; D003349:Cortisone Reductase