Concentration-dependent accumulation of [3H]-deltamethrin in sodium channel Nav1.2/β1 expressing Xenopus laevis oocytes

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 [3H]-DLT in non-transfected, sham (water)-transfected and VSSC (Nav1.2 + β1)-transfected oocytes after a 1 h exposure was measured using liquid scintillation counting. Successful transfection of Nav1.2 + β1 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 μM) induced tail currents in all VSSC-transfected oocytes; TTX also blocked these DLT-induced tail currents. In 0.1 μM DLT solution, non-transfected oocytes accumulated 0.098 ± 0.01 ppm [3H]-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 μM 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.