Concentration-dependent accumulation of [3H]-deltamethrin in sodium channel Nav1.2/beta1 expressing Xenopus laevis...

Disruption of neuronal voltage-sensitive sodium channels (VSSCs) by pyrethroid insecticides such as deltamethrin (DLT) has been widely studied using Xenopus laevis oocytes transfected with VSSC. However, the extent of pyrethroid accumulation in VSSC-expressing oocytes is unknown. Therefore, accumulation of [(3)H]-DLT in non-transfected, sham (water)-transfected and VSSC (Na(v)1.2+beta(1))-transfected oocytes after a 1h exposure was measured using liquid scintillation counting. Successful transfection of Na(v)1.2+beta(1) VSSCs in X. laevis oocytes was confirmed by two-electrode voltage-clamp; inward, tetrodotoxin (TTX)-sensitive currents were obtained in 98% of all oocytes examined (n=60 in nine experiments). DLT (1.0 microM) induced tail currents in all VSSC-transfected oocytes; TTX also blocked these DLT-induced tail currents. In 0.1 microM DLT solution, non-transfected oocytes accumulated 0.098+/-0.01 ppm [(3)H]-DLT, sham-transfected oocytes accumulated 0.06+/-0.01 ppm DLT, and VSSC-transfected oocytes accumulated 0.050+/-0.009 ppm DLT. In 1.0 microM DLT solution, non-transfected oocytes accumulated 0.62+/-0.08 ppm DLT, sham-transfected oocytes accumulated 0.60+/-0.09 ppm DLT, and VSSC-transfected oocytes accumulated 0.51+/-0.07 ppm DLT. There was a significant difference in DLT accumulation between VSSC-transfected oocytes and non-transfected controls, where the transfected oocytes consistently had less accumulation.