Effect of organophosphate pesticides on the activities of lecithin-cholesterol acyltransferase and cholinesterase in rat serum.

The lecithin-cholesterol acyltransferase activity in rat serum as well as that in human plasma was examined by using sonicated dispersions of lecithin and cholesterol mixtures as substrates. When dispersions with molar ratio of 1.2 and 5.9 were used as substrates, the acyltransferase activity in rat serum, in contrast to that in human plasma, was greater with the substrate dispersion having a molar ratio of 1.2 than with that of 5.9. In addition, the acyltransferase activity in rat serum with the dispersion having a molar ratio of 0.9 was inhibited upon addition of increasing amounts of lecithin, but that in human plasma for the same dispersion was stimulated and the maximum acyltransferase activity was obtained at a molar ratio of approximately 7. On the basis of these results, the inhibitory actions of organophosphate pesticides on the acyltransferase and cholinesterase in rat serum were investigated. The acyltransferase activity in rat serum was inhibited by the addition of 1×10-3M dimethyldichlorovinylphosphate (DDVP) and methylparathion. The decreased acyltransferase activity in rat serum was not restored by the addition of 1×10-3M 2-pyridine aldoxime methiodide (PAM). Similarly, cholinesterase activity in rat serum was almost completely inhibited by the addition of 1×10-5M DDVP. However, the decreased cholinesterase activity was restored by the addition of 1×10-3M PAM. In addition, the acyltransferase and cholinesterase activities in serum obtained from rats administered DDVP (35 mg/kg body) in vivo were inhibited to approximately 83-87% and 35-37% of those in control rat serum, respectively.