Multiple potassium and chloride channels in the human colon carcinoma cell line SW1116

SW1116 cells have a profound capacity for secreting mucin molecules bearing the Lewis^a epitope. Mucin molecules with the same epitope have been found to be elevated in the serum of patients with cystic fibrosis, a disease with defective ion channels. We therefore decided to study ion channels in this cell line. In the present work, we report the presence of two K⁺-channels and two Cl^-channels in the apical membrane of SW1116 cells. One of the K⁺-channels has a large conductance (~ 278 pS), anomalous rectifying properties, and is inactivated rapidly. The second type exhibited a linear I/V curve (19 pS), was voltage insensitive and inactivation was not observed. In cell-attached patches, spontaneous openings of chloride channels were seen with higher frequency than previously reported in other colon carcinoma cell lines or airway epithelial cells. Inside-out experiments allowed identification of two different Cl^--channels (Cl^--1 and Cl^--2). Both exhibited rectification, but in opposite directions, and both were insensitive to NIPAB.