Abstract:

The characteristics of Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase in mitochondria of Chilo suppressalis and inhibition of these two types of ATPases by nine common insecticides, i.e., deltamethrin, bifenthrin, cyfluthrin, cyhalothrin, salifluofen, endosufan, methamidophos, carbofuran and triazophos, were determined. The results indicated that the optimum pH value of Na⁺-K⁺-ATPase was 7.4, and the optimum temperature 37℃ for both Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase . The Michaelis constant (Km) of Na⁺-K⁺-ATPase hydrolyzing ATP was 0.42 mmol/L, not significantly different from that of Ca²⁺-Mg²⁺-ATPase (0.40 mmol/L). The maximum velocities (Vmax) hydrolyzing ATP were 302.47 nmol/(mg·min) for Na⁺-K⁺-ATPase and 128.04 nmol/(mg·min) for Ca²⁺-Mg²⁺-ATPase , respectively. When the final concentration of insecticides was 1×10^-4 mol/L, the order of inhibition of to Na⁺-K⁺-ATPase by five pyrethroids insecticides was deltamethrin> bifenthrin> cyfluthrin> cyhalothrin and salifluofen, The percentage of inhibition of Na⁺-K⁺-ATPase activity was 40.12%, 39.69%, 27.27%, 19.49%, and 18.71%, and the percentage of inhibition of Ca²⁺-Mg²⁺-ATPase was 29.27%, 23.78%, 19.88%, 11.64% and 14.34% by the above five pyrethroids respectively when the concentration of inhibitors was 1×10^-4 mol/L. The potential of endosufan inhibiting the Na⁺-K⁺-ATPase activity was same as its potential inhibiting Ca²⁺-Mg²⁺-ATPase , and the percentage of inhibition was 17.46%. Methamidophos and carbofuran possessed the potential of inhibition to Ca²⁺-Mg²⁺-ATPase , but no inhibition to Na⁺-K⁺-ATPase when their final concentration was 1×10^-4 mol/L. The inhibition of ATPase activity by nine insecticides was increased with the increasing of insecticide concentration from 1.6×10^-7  to 1×10^-4 mol/L. 

Key words: Chilo suppressalis, ATPase, insecticides, enzyme activity, inhibition