Human serum paraoxonase (PON1) activity in acute organophosphorous insecticide poisoning.

Human serum paraoxonase (PON1) and perhaps other mammalian paraoxonases catalyzes the hydrolysis of certain organophosphorus (OP) insecticides and nerve gases and so may alter significantly an individual's susceptibility to the toxicity of these chemicals. Serum PON1 exhibits a substrate dependent polymorphism and this polymorphism shows great interethnic variability. This study focused on the investigation of PON1, arylesterase and cholinesterase activities in 28 acute OP insecticide poisoning cases. Insecticide analysis were performed by GC-NPD and activities of enzymes were measured by using spectrophotometer. The activity levels for salt stimulated PON1, basal PON1 and arylesterase were found as 78.83 (35.39-186.13), 39.97 (2.49-80.43) micromol/min/l and 126.26 (36.34-288.24) mmol/min/l respectively. On the other hand the activity levels for butyrylcholinesterase (BTC) and acetylcholinesterase (AchE) were found as 797.23 (106.3-3823)U/l and 4.65 (0.21-30.29)U/ml. There was a correlation between percent stimulation of PON1 and BTC activities (r=0.446, P<0.05), but this correlation was lower than in cases who exposed to OP insecticides chronically. As a conclusion, in chronic and acute OP exposure, both PON1 level and phenotype must be taken into consideration.

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) 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.