Although these findings cannot be extrapolated to humans, MX should be studied as a candidate risk factor in the possible association between consumption of chlorinated drinking water and cancer in humans.

No abstract

1 Inhibition of cholinesterases (ChE) and carboxyles terases (CaE) by paraoxon (Px) was studied in vitro in the serum, liver, lung and muscle of mouse, guinea pig, rabbit and man (serum only). Moreover, the role ofPx hydrolyzing enzyme (Pxase) in the detoxification of Px was studied by inhibiting its activity with EDTA. 2 The ChE and CaE activities as well as their sensitivity to Px varied in different tissues and species. The ChEs were more sensitive than CaEs to Px except in the liver. The CaE activity in human and rabbit sera was low and resistant to Px, indicating that it may have a minor importance for the binding of Px. 3 The Px-inhibited ChEs were spontaneously reactivated in the mouse and rabbit sera during 24 h. In mouse, also the CaE activity was recovered. The presence of EDTA in the incubation medium prevented this reactivation indicating that Pxase takes part in the reactivation process. 4 In rabbit, the serum Pxase activity was very high suggesting a good Px detoxifying capacity of the rabbit serum. 5 The results show that amounts and sensitivities of esterases to OPs in rodents may markedly differ from that in man. Possible species-related differences in the affinity of ChEs and CaEs for OPs and the OP hydrolyzing activity should be taken into the con sideration, when animal data are extrapolated to man.

Vitamin E supplementation markedly decreased fish oil induced antioxidant enzyme activities in all tissues. Sparing of glutathione may be an important mechanism by which vitamin E decreased tissue protein oxidative damage.