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 synapse was studied under various experimental conditions to optimize these enzyme activities and to facilitate the studies of the mechanism of interaction of this pesticide with several components of this enzyme system. To obtain a clear-cut inhibition of this enzyme by deltamethrin the following conditions must be met: (a) the enzyme system should be purified by precipitation with ammonium sulfate (450 g litre^?1) prior to the addition of deltamethrin, (b) both Ca²⁺ and calmodulin (CaM) should be added to the incubated media before the addition of y-³²P]ATP, (c) deltamethrin should be incubated at least 10 min (but less than 30 min) with the enzyme system before y-³²P]ATP addition, (d) the incubation temperature should be above 20°C (optimum 30°C), (e) y-³²P]ATP concentration should be in the order of 10^? M (concentration adjusted using cold ATP), and (f) the incubation time with y^?P]ATP for incorporation of ³²P into the protein 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 of these active forms of pesticides was 1 R-deltamethrin > (S)(RS) fenvalerate ≥ p,p′-DDT. Other compounds were not active at the concentration tested, indicating the differential sensitivity of this enzyme and the existence of a correlation of inhibitory power to insecticidal activity.