The time course changes in serum concentrations of gonadotropin (GtH), 17α-hydroxypro-gestrone and 17α, 20β-dihydroxy-4-pregnen-3-one (17α, 20β-diOHprog) during LH-RH-induced final oocyte maturation and ovulation in gravid ayu Plecoglossus altivelis were examined. The fish underwent GVBD one day following a single intraperitoneal injection of emulsified LH-RH and ovulated in 2 days. A slow and moderate increase in serum levels of GtH occurred 1-3 days after injection. The LH-RH treatment caused a prompt increase in hte serum levels of 17α-hydroxypro-geterone and 17α, 20β-diOHprog concomitant with final oocyte maturation and ovulation. The levels of 17α, 20β-diOHprog remained high for 1-3 day after injection, followed by a sharp decrease at 5-7 days. The elevation of 17-hydroxyprogesterone, which is a precursor for 17α, 20β-diOHprog occurred earlier and persisted longer than the changes in 17α, 20β-diOHprog. Thus, the changes in serum levels of these steroids during final maturation and ovulation are medizted through the secretion of pituitary GtH. These findings suggest that 17α, 20β-diOHprog is the major ovarian mediator of LH-RH-induced oocyte maturation in ayu.
- Nippon Suisan Gakkaishi is an official journal of the Japanese Society of Fisheries Science written in Japanese only.
The society publishes an English journal, Fisheries Science, as well, which accepts submissions from non-members of the society over the world. Detailed information is available in http://jsfs.jp/en/journals/fisheries-science.