Effects of azamethiphos, an organophosphorus insecticide, on serum cholinesterase activity and isoenzymes in the rat.

The inhibitory effect of azamethiphos (Az), an organophosphorus insecticide, was detected in both the serum cholinesterase (ChE) activity and the ChE isoenzyme concentration in male Wistar rats. In our highest Az dosage group (270 mg/kg), following a single po administration, the serum ChE activity was significantly inhibited at 6 and 24 h post-Az administration. Five days after Az treatment, the ChE activity was still inhibited, but the observed difference was not statistically significant. The ChE activity increased to levels comparable to the control group by day 10. For the other Az-dosed groups, the ChE activities were inhibited only 6 h following administration. The serum ChE isoenzymes for all Az-dosed and control groups had 6 bands, indicating that Az did not effect the number of isoenzyme bands, indicating that Az did not effect the number of isoenzyme bands. However, Az had a significant effect on the ratios of the concentrations of these isoenzyme bands. The ratio of the main ChE isoenzyme bands (bands 5 and 6) was band 6 greater than band 5 for the young control group. As our control group aged, this ratio was reversed, with band 5 greater than band 6. For the highest Az dosage group (270 mg/kg), the ChE isoenzyme band ratio was band 5 greater than band 6 6 h after Az dosing. This proportion of band 6 decreased in parallel with an increase in band 5 during our 30-d experimental period. A correlation between the total ChE activity and ChE isoenzyme band 6 was found.