In vitro steroidogenesis by testicular fragments and ovarian follicles in a hybrid sturgeon, Bester

In this study, developmental changes in the steroidogenic capacity of testicular fragments and isolated ovarian follicles of a hybrid sturgeon, Bester, at a variety stage of developments were examined. Testicular fragments or isolated ovarian follicles were incubated in L-15 medium in the presence or absence of different concentrations of five preparations; forskolin, human chorionic gonadotropin (HCG), pregnenolone (P^sub 5^), 17α-hydroxyprogesterone (17αOHP) and testosterone (T) for 18 h at 15 °C. After incubation, concentrations of 11-ketotestosterone (11 KT) (testis) and, 17β-estradiol (E^sub 2^) (ovarian follicles) and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) (testis and ovarian follicles) were measured. 11KT was detected in the media following incubation with P^sub 5^, 17αOHP and T. Its concentration was higher during late spermatogenesis and prespermiation and lower at the degeneration stage. Both P^sub 5^ and 17αOHP were converted to DHP during the prespermiation stage. Forskolin had little stimulatory effect on the synthesis of 11KT and DHP and HCG did not induce the production of these steroids. E^sub 2^ was detected in the medium following incubation of follicles with P^sub 5^, 17αOHP and T at all stages of oocyte development. The concentration of E^sub 2^ in the medium increased during vitellogenesis with the peak production occurring at the tertiary yolk stage. In contrast, the potencies of follicles to produce steroids shifted to the production of DHP during migratory nucleus stage. Forskolin and HCG had little effect on the synthesis of E^sub 2^ and DHP. These results demonstrated that the failure of spontaneous spermiation or ovulation is not due to the insufficient synthesis of DHP, but may due to the lack of availability of precursors.[PUBLICATION ABSTRACT]