Toxicity of Progesterone in the New-Born Mouse. ∗

Abstract

Summary and Conclusions

The new-born mouse is highly susceptible to the toxic and lethal action of progesterone but, within 2 to 3 days, resistance develops rapidly, and by the 7th day the mouse can tolerate about 100 times as much progesterone as when one day old. Closely related steroids, at equivalent and even higher doses, do not cause the acute lethal action of progesterone in the new-born mouse. The report that progesterone given during the last third of gestation will cause fetal death has been confirmed, and it is suggested that this is due to a direct toxic effect of progesterone on the fetus. The rapid development of resistance to progesterone within a few days after birth suggests that a system or mechanism has appeared which is capable of detoxifying, catabolizing, counterbalancing or accelerating the excretion of progesterone.