title: Teleost maturation-inducing hormone, 17,20β-dihydroxypregn-4-en-3-one, peaks after spawning in Tinca tinca.
abstract: During an eight month study of the reproductive cycle in two age groups, and in both sexes, of tench (Tinca tinca L.), it was found that plasma concentrations of the presumptive 'maturation inducing hormone (MIH)' 17,20β-dihydroxypregn-4-en-3-one (17,20β-P) did not reach a peak during the spawning season, but as much as two months after spawning had ceased. The cessation of the spawning season was confirmed by histological examination of the gonads and by measurement of 11-ketotestosterone and 17β-estradiol in the plasma of males and females, respectively. Measurements were also made of the 'alternative MIH' 17,20β,21-trihydroxypregn-4-en-3-one in the older fish. However, this steroid did not show the same pattern as 17,20β-P. An assessment was made of the prevalence of primary spermatocytes in the testes of post-spawned fish - to test an alternative hypothesis that 17,20β-P might be involved in the stimulation of meiosis. However, there was no evidence for any increase in testis differentiation post-spawning. In fact the testes became increasingly undifferentiated as the autumn progressed. The role, if any, of this 'unseasonal' peak of 17,20β-P production remains to be determined.
authors.affiliation: Aristotle University of Thessaloniki, School of Biology, Department of Zoology, Thessaloniki, Greece. eantono@bio.auth.gr
authors.forename: Efthimia
authors.initials: E
authors.lastname: Antonopoulou
authors.forename: Athanassios C
authors.initials: AC
authors.lastname: Tsikliras
authors.forename: Martin
authors.initials: M
authors.lastname: Kocour
authors.forename: Vladimir
authors.initials: V
authors.lastname: Zlábek
authors.forename: Martin
authors.initials: M
authors.lastname: Flajšhans
authors.forename: David
authors.initials: D
authors.lastname: Gela
authors.forename: Veronika
authors.initials: V
authors.lastname: Piačková
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Scott
mesh_terms: D000818:Animals; D003530:Cyprinidae / Q000097:blood* / Q000502:physiology*; D004958:Estradiol / Q000097:blood; D005260:Female; D006908:Hydroxyprogesterones / Q000032:analysis / Q000097:blood*; D008297:Male; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D012741:Sexual Maturation / Q000502:physiology; D013739:Testosterone / Q000031:analogs & derivatives / Q000097:blood; D015854:Up-Regulation
chemical_list: D006908:Hydroxyprogesterones; C007433:17,20-dihydroxy-4-pregnen-3-one; D013739:Testosterone; D004958:Estradiol; C003600:11-ketotestosterone