Induction of Mid-term Abortion by Ricin A Chain in Mice

Ricin A chain, the potent inhibitor of protein synthesis, was evaluated for abortifacient activity using pregnant mice at mid-gestation. In a preliminary experiment, the intraperitoneal dose 50 µg per mouse killed all pregnant mice within 24 h with signs of vaginal bleeding and abortion. In subsequent experiments, pregnant mice given 100 ng each resulted in a decrease in maternal weight gain (48%, P<.05), while fetal weight showed a dose-related decrease of 19 and 22% in mice which received 50 or 100 ng respectively. In another experiment, the ricin A chain, administered as two successive doses (100 ng or 200 ng) on days 12 and 13 gestation, induced abortion in 16 to 67% of mice. At the same time 3 mice out of six, that received a dose of 100 ng/mouse lost w eight, whereas of those that received 200 ng. Four mice out of six lost weight and one died. Furthermore, laparotomized mice exhibited dead fetuses, separation of placenta and blood clots. These observations clearly indicate that the ricin A chain exhibits abortifacient effect, maternal and fetal toxicity in pregnant mice at mid-term.