Interference of parathion with mitochondrial bioenergetics.

The organophosphorus insecticide parathion depresses the phosphorylation efficiency of mitochondria as inferred from the decrease of RCR and ADP/O ratios. The transmembrane potential (delta psi) developed by energized mitochondria, and depolarization upon ADP addition are also decreased. Furthermore, repolarization is delayed and resumes at a slower rate. The inhibitory action of parathion on phosphorylation efficiency could be related with the following findings: (1) a direct effect on the succinate dehydrogenase-ubiquinone segment of the redox chain; (2) a direct action on the ATP synthetase complex; (3) partial inhibition of the phosphate transporter.