Toxicity and novel biomarkers of OP exposure

Abstract

This chapter consists of two different topics which are extremely important in the toxicity of organophosphorus (OP) compounds. The first part is concerned with OP toxicity in humans. OPs cause four important neurotoxic effects, including the cholinergic syndrome, the intermediate syndrome, OP-induced delayed polyneuropathy, and chronic OP-induced neuropsychiatric disorder. Compared with the cholinergic syndrome, that causes millions of cases of poisoning with fatality of more than 15% each year, other disorders involve much smaller number of patients. The second part describes the novel biomarker of OP exposure. Egasyn which is an isozyme of carboxylesterase is an accessory protein of β-glucuronidase (BG) in the liver microsomes. Egasyn-BG complex is located at the luminal site of liver microsomal endoplasmic reticulum membrane. When the OPs are incorporated into the liver microsomes, OP is tightly bound to egasyn, and subsequently, BG is dissociated and released into blood. Consequently, the increase of plasma BG activity is a good biomarker of OP exposure. The data presented in this chapter indicate the increase in plasma BG activity which is a much more sensitive biomarker to OP exposure than ChE (plasma cholinesterase) inhibition, particularly in the case of acute toxicity of OPs.