Inhibition of ovulation in the rabbit by the antimitotic agent, colchicine

This study establishes the optimum time to administer colchicine to inhibit ovulation in the rabbit, and it examines the effect of colchicine on prostaglandin biosynthesis in ovulatory follicles. Colchicine (2 mg/kg) was given at intervals ranging from 50 hours to 2 hours before ovulation. The ovulation efficiency was significantly reduced when colchicine was administered between 30 hours and 9 hours before ovulation, with maximum inhibition occurring at 20 hours before ovulation. Normal elevation in prostaglandin biosynthesis at the time of ovulation was significantly reduced when colchicine was given at 20 hours before ovulation, but not when it was given at 9 hours or 2 hours before ovulation. The results suggest that the mechanism by which the antimitotic agent colchicine inhibits prostaglandin biosynthesis and ovulation may be different from that of the nonsteroidal antiinflammatory agent indomethacin.