Correlation between the activity of liver enzymes and the LD50 of parathion in the rat

Abstract

A study was undertaken to investigate a possible correlation between the acute LD50 of parathion, in weanling and adult male and female rats, and the activity of the liver enzymes involved in the in vitro metabolism of parathion and its toxic oxygen analogue, paraoxon. A close relationship was found in adult male and female rats, as well as in adult females pretreated with phenobarbital, between the LD50 and the rate of in vitro degradation of parathion by the liver under experimental conditions in which both oxidative and hydrolytic metabolism occur. On the same basis, immature rats appeared to be more sensitive to parathion than was to be expected from the ability of their livers to metabolize parathion in vitro. It is concluded that the rate of in vitro degradation of parathion by the liver is a satisfactory index of the in vivo toxicity of parathion in adult rats, but not in immature animals.