[The activity of blood cholinesterase in rats exposed to dimehypo]

To determine whether and to what degree the activity of cholinesterase(ChE) is inhibited by dimehypo at different doses of dimehypo [scientific name: 2-dimethylamine-1,3-bi(sodium hyposulfit)].

Rats were dosed with dimehypo or methamidophos orally, and were randomly divided into four subgroups according to the pesticide doses, which were 1/16, 1/8, 1/4 and 1/2 of LD50 respectively(the LD50 of dimethypo and methamidophos is 342 mg/kg and 20 mg/kg respectively). The activity of ChE in blood was determined before and 30 min, 1, 2, 4 and 24 h after exposure. The modified Ellman Method was employed to measure the activity of ChE.

1/16 LD50 dose of dimehypo did not affect the activity of ChE. When the dose increased, the activity of ChE decreased accordingly. 1/2 LD50 dose of dimehypo inhibited the activity of ChE by 35.9% compared with that of control group(P < 0.01). In rats dosed with methamidophos, even 1/16 LD50 dose inhibited the activity of ChE by 42.4% compared with that of control group. When the dose of methamidophos increased, the activity of ChE decreased accordingly. 1/2 LD50 dose of methamidophos inhibited the activity of ChE by 52.9%. The activity of ChE in the rats dosed with dimehypo at various doses was significantly lower than that in the rats dosed with corresponding doses of methamidophos(P < 0.01).

Higher doses of dimehypo may inhibit the activity of ChE. However, as compared with methamidophos, dimehypo is a weaker inhibitor of ChE.