Serum paraoxonase (PON1) isozymes: the quantitative analysis of isozymes affecting individual sensitivity to environmental chemicals.

In a recent study on Gulf War veterans who developed delayed neurotoxicity symptoms, we found their levels of serum paraoxonase (PON1) isozyme type Q to be significantly lower than in the control, unaffected veteran group. These results were obtained in 25 ill veterans and 20 well control subjects, of which 10 were deployed and 10 were nondeployed battalion members who remained in the United States during the Gulf War. The blood samples were also assayed for serum butyrylcholinesterase in our laboratory, and more recently in Dr. C. Broomfield's laboratory for somanase and sarinase activities. The cholinesterase activities showed no significant correlation with the PON1 isozyme levels or the severity of the clinical symptoms, but the somanase and sarinase levels ran parallel to the PON1 type Q isozyme concentrations. Although there is no direct evidence that these Gulf War veterans were directly exposed to or encountered either of these nerve gases, they may have been exposed to some environmental or chemical toxin with a similar preference for hydrolysis by the PON1 type Q isozyme. The number of subjects is relatively small, but the results should encourage other investigators to examine both the individual phenotypes and the levels of PON1 isozymes in other groups exhibiting neurological symptoms.