Acetylcholine-activated chloride current in the T-84 colonic cell line

Abstract

 The stimulation of epithelial chloride secretion by hormones and neurotransmitters involves the activation of apical membrane chloride channels. The regulation of chloride current by acetylcholine in the T-84 colonic cell line was investigated using single-channel patch-clamp techniques. Treatment with carbachol resulted in the stimulation of transient chloride currents in 18 of 32 previously quiescent patches. Lack of resolvable single-channel openings suggests that single-channel conductance is less than 5-pS. Of 18 responsive patches, 4 showed multiple current oscillations. Treatment of the cells with AlF₄ ^– activated sustained chloride currents, suggesting that G proteins are involved. In excised patches, chloride current was markedly sensitive to free Ca²⁺ concentrations between 500 and 1000 nM. Time-dependent activation and inactivation of chloride current occurred at +60 and –60 mV. These results indicate that the chloride channels responsible for cholinergic activation of chloride conductance in the T-84 colonic cell line are members of the very low conductance family of chloride channels.