IN-VITRO BIOSYNTHESIS OF ESTRADIOL-17-BETA AND 17-ALPHA,20-BETA-DIHYDROXY-4-PREGNEN-3-ONE BY VITELLOGENIC OVARIAN FOLLICLES FROM MIGRATING NEW-ZEALAND LONGFINNED EELS (ANGUILLA-DIEFFENBACHII)

In vitro oestradiol-17 beta (E(2)) and 17 alpha,20 beta-dihydroxy-4-pr egnen-3-one (17,20-DHP) production by vitellogenic ovarian tissue from Anguilla dieffenbachii captured during the natural spawning migration was examined. Ovarian fragments were incubated with or without human chorionic gonadotropin (hCG) in the presence or absence of pregnenolon e, androstenedione or testosterone. Despite relatively high E(2) level s in vivo (2.48+/-0.28 ng ml(-1), n=7), in vitro E(2) production was l ow. In contrast, 17,20-DHP levels were low in vivo (less than 0.16 ng ml(-1)), while production was high in the presence of pregnenolone in vitro, indicating strong 20 beta-hydroxysteroid dehydrogenase activity in vitellogenic follicles. Addition of hCG did not significantly stim ulate E(2) or 17,20-DHP production above that of controls in any of th e incubations. These results are in contrast to those arising from sim ilar studies in salmonids and indicate that the models developed for c ontrol of E(2) and 17,20-DHP production by the salmonid follicle may n ot be fully applicable to the eel follicle.