Organophosphate detoxication potential of various rat tissues via A-esterase and aliesterase activities.

Paraoxon and chlorpyrifos-oxon, active metabolites of the organophosphorus insecticides parathion and chlorpyrifos, can be detoxified via A-esterases and aliesterases. These enzyme activities were measured in various tissues of Sprague-Dawley rats. High A-esterase activities were detected in liver, serum and liver mitochondrial/microsomal fractions. Low or no A-esterase activities were detected in other tissues and tissue fractions. A-Esterase substrate:substrate activity ratios suggest that the substrates are probably not degraded by the same enzyme. Highest aliesterase activities were observed in the small intestine and liver with moderate activity in kidney, serum and lungs. Low activities were noted in brain, spleen and skeletal muscle.