THE ROLE OF MICROSOMAL MIXED FUNCTION OXIDASES IN THE METABOLISM AND MECHANISM OF ACTION OF CERTAIN ORGANOPHOSPHORUS INSECTICIDES

: The influence of microsomal mixed function oxidases (MFO) on the biotransformation of pesticides was investigated in experiments with perfusion of isolated rat livers and in whole animals. The pesticides examined were 3 organophosphorus insecticides (OP): S-propyl-O-phenyl-O-ethylthiophosphate (heterophos), a mixture of O,O-dimethyl-O-cyclohexylthionphosphate and O,S-dimethyl-O-cyclohexylthiolphosphate (cyclophos), and dithiophosphonate. The indices of NADPH-dependent hydroxylating systems measured in the microsomal fraction of rat liver homogenates were the activity of aniline hydroxylase, aminopyrine demethylase and the amount of cytochrome P-450. It was shown that not only did the specific chemical structure of the OP and induction or inhibition of MFO determine OP activation and detoxification (and thus its biological action), but also the route and frequency of exposure could influence these parameters.