Effects of pH on in vitro ovulation of goldfish (Carassius auratus) oocytes.

The in vitro effects of pH on goldfish (Carassius auratus) ovulation were investigated. Final oocyte maturation and follicular detachment were induced in vivo in gravid goldfish by HCG injections and elevated holding temperatures. Females were biopsied to determine the time of germinal vesicle breakdown and when oocytes should be removed for in vitro incubations. Prior to ovulation, the ovaries were removed, dissected and mature intrafollicular oocytes were incubated in media of varying pH (7.3-8.9). There was a significant increase in ovulation as the pH of the incubation increased and this ovulation could be blocked by indomethacin. Indomethacin did not inhibit the actual mechanism of oocyte expulsion since exogenous PGF2 alpha induced ovulation in indomethacin blocked incubates. Increased pH did not increase the ovulatory response observed with exogenous PGF2 alpha. The combined results suggest that an increase in incubation pH stimulates prostaglandin synthesis that, in turn, stimulates ovulation.