Responses of Cell Cultures to Insecticides. IV. Relative Toxicity of Several Organophosphates in Mouse Cell Cultures. ∗

Abstract

Summary

Mouse liver NCTC #1469 and mouse skin L-929 strain cells vary markedly in their susceptibility to organophosphorus insecticidal compounds. In mouse liver cells, the 50% growth inhibitory level of cytotoxicity was measured as 1804 μg/ml of medium for malathion, 310 μg/ml for Cygon®, 11 μg/ml for DI-Syston®, and 2 μg/ml for Dipterex®. The low toxicity of malathion to mouse liver cells correlates well with its low toxicity to the mouse but contrasts with its high toxicity to human liver Chang strain cells. Mouse liver cells were more susceptible to malaoxon than to malathion, but human liver cells were almost equally susceptible to malaoxon and malathion. Differences in cell susceptibility are largely due to the rates of malathion biotransformation to malaoxon, a more toxic and more potent acetylcholinesterase inhibitor. When tested at concentrations below acute toxicity levels, malathion, Cygon, and DI-Syston stimulated mouse liver cell growth.