Cytoskeletal modulation of sodium current in human jejunal circular smooth muscle cells

ANa⁺ current is present in human jejunal circular smoothmuscle cells. The aim of the present study was to determine the role ofthe cytoskeleton in the regulation of the Na⁺ current.Whole cell currents were recorded by using standard patch-clamptechniques with Cs⁺ in the pipette to block K⁺currents. Cytochalasin D and gelsolin were used to disrupt the actincytoskeleton and phalloidin to stabilize it. Colchicine was used todisassemble the microtubule cytoskeleton (and intermediate filaments)and paclitaxel to stabilize it. Acrylamide was used to disrupt theintermediate filament cytoskeleton. Perfusion of the recording chamberat 10 ml/min increased peak Na⁺ current recorded fromjejunal smooth muscle cells by 27 ± 3%. Cytochalasin D andgelsolin abolished the perfusion-induced increase in Na⁺current, whereas incubation with phalloidin, colchicine, paclitaxel, oracrylamide had no effect. In conclusion, the Na⁺ currentexpressed in human jejunal circular smooth muscle cells appears to beregulated by the cytoskeleton. An intact actin cytoskeleton is requiredfor perfusion-induced activation of the Na⁺ current.