Paraoxonase and Acetylcholinesterase Activities in Humans Exposed to Organophosphorous Compounds

Abstract

Different kinds of organophosphorous compounds (OP) are used as pesticides in Turkish agriculture. Suicidal, accidental, or occupational exposure may occur in developing countries. OP inhibit acetylcholinesterase (AChE) activities; on the other hand, serum paraoxonase (PON1) hydrolyzes the toxic metabolites of a variety of OP. In recent years, some studies have shown that PON1 activity is an important marker in individuals who are exposed to OP. Both serum cholinesterase and PON1 activities were measured spectrophotometrically from 18 male agricultural workers who were chronically exposed to azinphos methyl, chlorpyriphos, or malathion and other pesticides during cereal spraying, transportation, and storage. The individuals were classified according to PON1 phenotypes using the antimode 60% stimulation method to determine the dividing point between non-salt-stimulated, A type (homozygotes for the low-activity allele), and salt-stimulated AB (heterozygotes) and B types (homozygotes for the high-activity allele). A positive correlation was found between AChE activities and percent of PON1 stimulation. The individuals with phenotype A had the lowest enzyme activities. This study suggests that individuals with phenotype A might be more sensitive to OP-induced toxicity.

Acute effects of different doses of malathion on the rat liver

“…Akgür et al . also reported that chronic administration of organophosphate did not reveal a significant correlation between paraoxonase activity and AChE [6]. It is reported that paraoxonase plays a more effective role in acute organophosphates poisoning than chronic organophosphate poisoning [29].…”

“…Experimental studies showed that chronic administration of organophosphates resulted in an increase in serum TNF-α levels and inflammation in rats’ brain, Langerhans islets, and macrophages [6]. Gordon and Rowsey reported that acute administration of chlorpyrifos gave rise to an increased serum TNF-α level [30].…”

“…Paraoxonase is an antioxidant enzyme used in the detoxification of lipid peroxidation. Paraoxonase plays an active role in reducing the toxic effects of organophosphate compounds and nerve gases by hydrolyzing them [6]. Arylesterase catalyzes the hydrolysis of 1-phenyl acetate and it is also reported that arylesterase is a protective enzyme against oxidative stress along with paraoxonase [7].…”