Effect of neferine on toxicodynamics of dichlorvos for inhibiting rabbit cholinesterase.

AIM: To study the effect of neferine (Nef) on toxicodynamics of dichlorvos (DDVP) for inhibiting the rabbit cholinesterase (ChE) and search the relativity between in vivo and in vitro reactivating effect of Nef. METHODS: Calorimetric method was used to determine the blood concentraiton of DDVP, and 3P97 software was used to calculate the parameters of toxicokinetics. Ellman's method was used to determine the ChE activity in plasma. The toxicodynamics curve in vivo and the concentration-effect curve in vitro were drawn to compare the effects of Nef on these two curves. RESULTS: In the rabbit poisoned by ig DDVP 12.5 mg/kg there was almost no effect of Nef on the toxicokinetics of DDVP. The slope of toxicodynamics curves for depressed ChE increased about 3 times after treatment with Nef 7.5 mg/kg and pyratoxime methylchloride (2-PAM Cl) 50 mg/kg, compared with the untreated group, there was a higher significant difference (P<0.01). In vitro Nef shifted the cumulative concentration-effect curve of DDVP on ChE to the right and decreased the maximal inhibitory effect obviously. The shift tendency of concentration-effect curve for DDVP in vitro was similar to that of the curve in vivo, difference between their value b was not significant (P>0.05). CONCLUSION: Nef reactivates the ChE depressed by DDVP. The experiment in vitro may be used as a preliminary index to observe the reactivation of ChE inhibited by anticholinesterases.