In vitro steroid production by triploid ovarian follicles.
Triploid female fish are unlike normal diploids in that they show impaired oocyte growth and are unable to produce viable offspring. Compared to diploid siblings, triploid female brook trout (Salvelinus fontinalis) have significantly lower levels of plasma vitellogenin, testosterone (T), and estradiol-17beta (E(2)), and show significantly lower gonadosomatic indices. The purpose of this study was to compare in vitro steroid production by diploid and triploid ovarian follicles in order to determine whether delayed oocyte growth in triploids is the result of a decreased capacity for E(2) synthesis by triploid follicles. Intact oocytes (i.e., including follicular tissue) from several age 3(+) triploids were pooled and sorted according to small (<2mm), medium (2.2-3.0mm), and large (4.0-5.0mm) diameter size, and compared to same-sized vitellogenic oocytes from 3(+) diploids. Oocytes were incubated for 8h at 15 degrees C in the presence or absence of gonadotropin stimulus (SG-G100) and the precursors E(2), T, and cholesterol. Estradiol-17beta output following SG-G100 treatment was significantly higher than in controls for both diploid and triploid follicles. Production of E(2) was dependent on stage of oocyte and follicular development in triploids, with triploid and diploid follicles of similar diameter producing similar amounts of E(2) with SG-G100 stimulus. This suggests that ovarian steroidogenesis is similar in diploids and triploids.
Schafhauser-Smith
D
D
Department of Biology, University of New Brunswick, Fredericton, NB, Canada E3B 6E1.
Benfey
T J
TJ
D000818:Animals; D002784:Cholesterol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000096:biosynthesis*; D005260:Female; D005399:Fishes; D006062:Gonadotropins / Q000494:pharmacology; D066298:In Vitro Techniques; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology*; D011123:Polyploidy; D011863:Radioimmunoassay; D013739:Testosterone / Q000494:pharmacology; D014337:Trout; D014819:Vitellogenins / Q000378:metabolism
D006062:Gonadotropins; D014819:Vitellogenins; D013739:Testosterone; D004958:Estradiol; D002784:Cholesterol