PROTECTIVE EFFECT OF PRALIDOXIME ON MUSCLE-FIBER NECROSIS INDUCED BY ORGANOPHOSPHATE COMPOUNDS

Objective: To determine the protective effect of pralidoxime on muscle fiber necrosis induced by organophosphate acute intoxication in rats. Design: Adult male Wistar rats were given oral organophosphate compou nds dissolved in glycerol formal: dichlorvos, isofenphos, metamidophos , and diazinon, Half of the animals also received pralidoxime mesylate (20 mg/kg, intraperitoneal). Control animals received only the solven t. Twenty-four hours after treatment, the diaphragm muscle was collect ed for histological counts of necrotic muscle fibers in transverse sec tions. Results: Metamidophos- and isofenphos-treated animals showed th e highest percentage of necrotic muscle fibers: 1.66 +/- 1.112 and 1.3 4 +/- 0.320, respectively, Diazinon-treated animals had a lower percen tage of necrotic fibers: 0.40 +/- 0.032 (p < 0.05) compared to the fir st 2 products, and dichlorvos-treated animals showed the smallest: 0.0 5 +/- 0.021 (p < 0.05) when compared to the other 3 products. Pralidox ime reduced necrotic fibers about 20 times in metamidophos-treated ani mals, 10 times in isofenphos-treated animals and 6 times in diazinon-t reated animals. Pralidoxime administration did not increase plasma cho linesterase activity in any group, although symptoms were reduced, Con clusions: Grime reduced diaphragmatic muscle necrosis in experimental organophosphate intoxication, despite little effect on plasma cholines terase. Since respiratory insufficiency is an important cause of morta lity and morbidity in organophosphate intoxications, early oxime admin istration may be particularly beneficial.