M. Hitchcock, S. D. Murphy
Sep 1, 1967
Citations
0
Influential Citations
45
Citations
Quality indicators
Journal
Biochemical pharmacology
Abstract
Abstract The reduction of the 4-nitro group of O,O-(4-nitrophenyl) phosphorothioate (parathion), O,O-diethyl O-(4-nitrophenyl) phosphate (paraoxon), and O-ethyl O-(4-nitrophenyl) benzene thiophosphonate (EPN) to the corresponding amino group was studied in vitro in tissues from mammalian, avian, and piscine species. The properties of the enzyme system that catalyzed the reduction of these insecticides were similar to those of previously reported enzyme systems which reduce ρ-nitrobenzoic acid. When NADPH and FAD were used as cofactors, the mitochondrial, microsomal, and soluble fractions contained, respectively, 34, 38, and 27 per cent of the parathion nitroreductase activity of rat liver whole homogenate. The capacities of liver homogenates from various species of the three classes of animals to reduce parathion and EPN were compared. Considerable variation in enzyme activity among a given class of animals as well as among the three classes was observed. For all species, the amount of EPN reduced was less than 25 per cent of the amount of parathion. Enzymatic activity was also present in mammalian kidneys, spleens, hearts, lungs, and erythrocytes, and also in avian kidneys. The contribution of reduction to the total inactivation of paraoxon, as measured by loss of anticholinesterase activity, was compared in rat, guinea pig, and chicken liver homogenates. Formation of aminoparaoxon by rat and chicken livers accounted for over half and guinea pig livers for a quarter of the total loss of anticholinesterase activities of the incubates.