ACTION OF DELTAMETHRIN ON THE CALCIUM CALMODULIN-DEPENDENT PROTEIN-KINASE FROM THE RAT-BRAIN

The action of deltamethrin on the calcium/calmodulin-dependent protein kinase (CaM-Kinase II) and phosphatase system in the rat brain synaps e was studied under various experimental conditions to optimize these enzyme activities and to facilitate the studies of the mechanism of in teraction of this pesticide with several components of this enzyme sys tem. To obtain a clear-cut inhibition of this enzyme by deltamethrin t he following conditions must be met: (a) the enzyme system should be p urified by precipitation with ammonium sulfate (450 g titre-1) prior t o the addition of deltamethrin. (b) both Ca2- and calmodulin (CaM) sho uld be added to the incubated media before the addition of [gamma-P-32 ]ATP. (c) deltamethrin should be incubated at least 10 min (but less t han 30 min) with the enzyme system before [gamma-P-32]ATP addition. (d ) the incubation temperature should be above 20-degrees-C (optimum 30- degrees-C), (e) [gamma-P-32]ATP concentration should be in the order o f 10(-8) M (concentration adjusted using cold ATP), and (f) the incuba tion time with [gamma-P-32]ATP for incorporation of P-32 into the prot ein should be in the neighborhood of 60 s. Under these conditions. the inhibitory potency of various active and inactive isomers or analogs of pyrethroids and DDT was tested. The order of the inhibitory power o f these active forms of pesticides was IR-deltamethrin > (S)(RS) fenva lerate greater-than-or-equal-to p,p'-DDT. Other compounds were not act ive at the concentration tested. indicating the differential sensitivi ty of this enzyme and the existence of a correlation of inhibitory pow er to insecticidal activity.