Termination of pregnancy in rabbit and mouse by Trichosanthin

The effects of a single intraperitoneal injection of Trichosanthin in 6-, 10-, 17- or 22-day pregnant rabbit (2 mg/rabbit) or in 11-day pregnant mouse (50 micrograms/mouse) were studied. Trichosanthin induced abortion in 100% of the 17- or 22-day pregnant rabbits within 48-72 hours and decreased circulating progesterone (delta 4P)concentrations with 24 hrs. On the other hand, the same dose failed to terminate pregnancy in 6- or 10-day pregnant rabbits and caused no significant changes in circulating delta 4P levels. Exogenous delta 4P or prolactin + human chorionic gonadotropin given twice daily failed to reverse the Trichosanthin-induced termination of pregnancy. However, this resulted in a delay of fetal expulsion. It is concluded that Trichosanthin-induced termination of pregnancy is not solely a result of luteolysis but is likely to be due to its toxic effects on placenta, embryo or both. A dose of 50 microgram Trichosanthin given to 11-day pregnant mice resulted in a termination of pregnancy within 96 hours and also a significant decrease in delta 4P levels in 24 hrs. The ratio of delta 4P to 20 alpha-dihydroprogesterone was also decreased steadily after Trichosanthin administration.