Abstract
Changes in plasma gonadotropin (GtH) and steroid hormone levels were investigated during ovulation induced by human chorionic gonadotropin (HCG) in female goldfish. Sexually mature female goldfish maintained at 20°C under 14L10D (lights on at 0430hr) were injected with HCG at a dose of 10IU/g BW at 2100hr. Twenty-one fish out of 28 ovulated between 9 and 18 hours (0600 to 1500hr) after injection. In ovulatory fish, there was neither a significant increase nor surge in plasma GtH levels after the injection, whereas plasma testosterone and 17α, 20β-dihydroxy-4-pregnen-3-one levels showed changes similar to those occurring in spontaneous ovulation. These results suggest that injected HCG acts directly on the ovary without accelerating endogenous GtH secretion, and therefore induces ovulation in a similar manner as does the ovulatory GtH surge in spontaneous ovulation.
