Effect of malathion on nucleic acid synthesis in phytohemagglutinin-stimulated human lymphocytes.

The effect of malathion, an organophosphorus insecticide, on DNA and RNA synthesis was investigated by measuring the rate of incorporation of 3H thymidine and 3H uridine, respectively, into human lymphocytes stimulated by phytohemagglutinin (PHA). Increasing concentrations of malathion, from 10 to 70 micrograms/ml, were added to human lymphocyte cultures at different times in relation to PHA introduction. The lowest applied dose of malathion (10 micrograms/ml) in most cases led to increased incorporation of both 3H thymidine and 3H uridine. Higher concentrations of malathion (30, 50, 70 micrograms/ml) caused a time- and dose-dependent decrease of radioisotope incorporation.