Toxicity of Progesterone in the New-Born Mouse.

Abstract

The new-born mouse is highly susceptible to the toxic and lethal action of progesterone but, within 2-3 days, resistance develops rapidly, and by the 7th day the mouse can tolerate about 10U times as much progesterone as when 1 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.