Paraoxonase and acetylcholinesterase activities in humans exposed to organophosphorous compounds

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) activ ities; on the other hand, serum paraoxonase (PON1) hydrolyzes the toxic met abolites 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 spectrophotomet rically from 18 male agricultural workers who were chronically exposed to a zinphos methyl, chlorpyriphos, or malathion and other pesticides during cer eal spraying, transportation, and storage. The individuals were classified according to PON1 phenotypes using the antimode 60% stimulation method to d etermine the dividing point between non-salt-stimulated, A type (homozygote s 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 indi viduals with phenotype A had the lowest enzyme activities. This study sugge sts that individuals with phenotype A might be more sensitive to OP-induced toxicity.