engleski

Kinetics of acethylcholinesterase inhibition by dichlorvos and terbufos in rat brain

The exposure to organophosphorus pesticides lead to cholinesterase inhibition and cause an accumulation of acetylcholine in the central nervous system. The effect of dichlorvos (2,2-dichlorovinyl dimethyl phosphate) and terbufos (S-tert-butylthiomethyl-O,O-diethyl phosphorodithioate) on the activity of acetylcholinesterase (AChE) in male rat brain cytosol was studied. The K_M and v_max values for AChE were determined (K_M 4,21-7,46 x 10^-5 M; v_max 0,0221-0,0356 x 10^-6 mol min^-1 mg^-1). Activity of AChE was measured by the method of Ellman et al.^1. In vitro the influence of the various concentrations of dichlorvos (0,0025-0,1000 mM) and terbufos (0,01-0,25 mM) were studied. For dichlorvos v_max value was 0,0259ą0,0003 x 10^-6 mol min^-1 mg^-1 and K_M 0,354-0,416 x 10^-3 M, and for terbufos vmax 0,0208ą0,0014 x 10^-6 mol min^-1 mg^-1 and K_M 0,0457-0,1757 x 10^-3 M. A kinetic study of in vitro inhibition of AChE in the rat brain by dichlorvos and terbufos showed its competitive nature. K_i values were for dichlorvos 0,0059 x 10^-3 M and for terbufos 0,114 x 10^-3 M. Hill"s coefficients (n_H) were for dichlorvos 1,01 and for terbufos 0,92, that suggested one molecule of compound reacted with one molecule of AChE. Values of I_50 were for dichlorvos 3,14 microM and for terbufos 220,33 microM. References: 1. Ellman, G.L., Courtney, K.D., Andres, V., Featherstone, R.M., Biochem. Pharmacol. 7 (1961) 88.

acethylcholinesterase; dichlorvos; terbufos; rat brain

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