Lactate dehydrogenase isoenzymes in mammalian cells exposed to isophenphos

The cytotoxicity of isophenphos, an organophosphorus insecticide that has the potential to cause delayed polyneuropathy, was evaluated in GBK and V79 cells. A 72 h time course following isophenphos exposure indicated a dose-dependent growth inhibition as determined by cell counts. The administration of isophenphos (20 g/ml) to GBK cells cultured at high densities indicated a decrease in the activities of LDH isoenzymes. Analysis of V79 cells revealed a decrease of LDH3, the only LDH isoenzyme detected in these cells.