Effects of methylene chloride on body and organ weight and plasma butyrylcholinesterase activity in mice.

Exposure to methylene chloride produced a time and concentration related increase in liver weight. The effect was more prominent in female mice than in male. The activity of plasma butyrylcholinesterase (BuChE) increased even more than the liver weight at corresponding exposures, but only in the males. Fatty infiltration was noticeable after exposure to 75 p.p.m. and was more prominent in the females than in the males. Thirty to 60 days of continuous exposure were required to reach stable maxima. Intermittent exposure was less effective than continuous exposure in producing the effects. Most effects were fully reversible after exposure for both 30 and 90 days if the animals were transferred to a solvent-free environment. However, after exposure for 90 days, BuChE activity in the males did not return to normal within 30 days but after 90 and 120 days free from exposure only slight if any effects on BuChE activity remained.