1Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, Kanagawa 252-8510, 2Department of Fisheries, School of Marine Science and Technology, Tokai University, Shizuoka 424-8610, Japan
The ice goby is an anadromous fish, and females enter the river with yolk-accumulated ovaries. Vitellogenesis once stop in the river, and the ovaries rapidly develop in the nest before spawning. To clarify the endocrinological mechanisms of this discontinuation of yolk production and accumulation, effects of gonadotropins (GTHs) on estradiol-17β (E2) production were investigated in vitro, using the ovaries of females captured in the river.
Of GTHs tested, salmon pituitary extract (SPE) was effective in E2 production at higher doses (1-10μg/mL). Human chorionic gonadotropin and pregnant mares' serum gonadotropin also showed a significant effect (1-10I.U./mL). Actinomycin D and cycloheximide significantly inhibited E2 production stimulated by SPE. In the absence of GTHs (control group) ovary fragments produced only a marginal amount of E2. Addition of testosterone to the control group was of no effect.