Influence of X-Radiation on Development of Enzymes Responsible for Desulfuration of an Organic Phosphorothioate and Reduction of p-Nitrobenzoic Acid in the Livers of Male Rats

Abstract

The available information on the susceptibility of irradiated animals to various drugs and toxic agents indicates that radiation does not affect the ability of adult animals to detoxify most foreign chemicals. Recent studies in this laboratory (1), however, have demonstrated that young male rats develop marked resistance to the toxicity of a cholinergic organic phosphate, 0,0-diethyl 0-(4-methylthio)-m-tolyl phosphorothioate (DMP), between 23 and 45 days of age and that exposure of the animals to sublethal doses of X-radiation inhibits development of this resistance. Our preliminary studies with this cholinergic organic phosphate indicated that Xradiation inhibits development of a system responsible for the metabolism of this compound but does not affect the activity of the system after it reaches the adult level. The enzymes responsible for the metabolism of many foreign compounds are located primarily in the microsome fraction of the liver, and they develop after birth of animals (2). The present study was undertaken to extend our preliminary observations on the influence of X-radiation on the development of enzymes in the livers of young male rats. The influence of radiation on an enzyme responsible for desulfuration of a cholinergic organic phosphorothioate was studied by measuring the amount of Guthion converted to its oxygen analog (3, 4). The reduction of p-nitrobenzoic acid to p-aminobenzoic acid was used as a measure of reductase activity. These enzymes are located, for the most part, in the microsome fraction of the liver (4, 5). The results of this study demonstrated that sublethal doses of X-ray cause a marked inhibition of development of the system responsible for the desulfuration of Guthion to its oxygen analog but do not influence development of reductase activity in the livers of young rats.