Modification by pyrethroids and DDT of phosphorylation activities of rat brain sodium channel

The effects of pyrethroids and DDT on the alpha-subunit protein of the rat brain sodium channel were studied by using both native and exogenously added cAMP-dependent protein kinases. For this purpose, the sodium channel was partially purified, using the method of Hartshorne and Catterall [J Biol Chem 259: 1667-1675, 1984], and 32P-phosphorylated using [gamma-32P]ATP and exogenously added catalytic subunit of cAMP-dependent protein kinase. By comparing the phosphorylation patterns of the isolated sodium channel to those of the partially purified or unpurified (i.e. intact synaptosomes) preparations, it was concluded that the alpha-subunit of the voltage-sensitive sodium channel protein is the only phosphorylatable protein present at the 260 kD molecular weight range on the sodium dodecyl sulfate-polyacrylamide gel electrophoretogram. Phosphorylation of the alpha-subunit was induced by depolarization, and this process was inhibited by 10(-6) to 10(-10) M 1R-deltamethrin, but not by 1S-deltamethrin, the latter being an inactive enantiomer of the former. DDT produced a similar effect, but only at a higher concentration range. By using lysed synaptosomal membranes, it was possible to study the direct effects of these compounds on the alpha-subunit, which were similar to those produced by depolarization of intact synaptosomes.