Lipid peroxidation and changes in cytochrome c oxidase and xanthine oxidase activity in organophosphorus anticholinesterase induced myopathy.

A possible role of radical oxygen species (ROS) initiated lipid peroxidation in diisopropylphosphorofluoridate (DFP)-induced muscle necrosis was investigated by quantifying muscle changes in F2-isoprostanes, novel and extremely accurate markers of lipid peroxidation in vivo. A significant increase in F2-isoprostanes of 56% was found in the diaphragm of rats 60 min after DFP-induced fasciculations. As possible source of ROS initiating lipid peroxidation, the cytocrome-c oxidase (Cyt-ox) and xanthine dehydrogenase-xanthine oxidase (XD-XO) systems were investigated. Within 30 min of onset of fasciculations Cyt-ox activity was reduced by 50% from 0.526 to 0.263 mumol/mg prot/min and XO activity increased from 0.242 to 0.541 mumol/mg prot/min. Total XD-XO activity was unchanged, indicating a conversion from XD into XO. In rats pretreatment with the neuromuscular blocking agent d-tubocurarine, prevented DFP-induced fasciculations, increases in F2-isoprostanes and changes in Cyt-ox or XD-XO. The decrease in Cyt-ox and increase in XO suggest that ROS are produced during DFP induced muscle fasciculations initiating lipid peroxidation and subsequent myopathy.