cAMP-induced chloride transport in NCL-SG3 sweat gland cells

cAMP-induced ion transport in a human sweat gland cell line, NCL-SG3, was investigated by X-ray microanalysis and patch-clamp technique. Stimulation with cAMP caused a decrease in the cellular Cl and K. cAMP had no significant effect on the intracellular Na and Ca. Chloride channel blockers (9-AC, DPC and NPPB) inhibited the cAMP-induced chloride efflux. In patch-clamp experiments the inward current increased over a period of 5-15 min on addition of membrane-permeable cAMP in 66% of the attempts when the cell was held at 0 mV and pulsed to negative membrane potentials. The inward current was completely blocked by chloride channel blockers. Washout reversed the effect of cAMP. The inward current was not diminished by substitution of impermeable cations for Na in the bath and was insensitive to TEA (tetraethylammoniumchloride). It is concluded that the inward current is mainly a chloride current. Cystic fibrosis transmembrane regulator (CFTR) could not be demonstrated in the NCL-SG3 cells. It is therefore possible that the chloride efflux is mediated by other types of chloride channels.