A K(+)-selective channel in the colonic carcinoma cell line: CaCo-2 is activated with membrane stretch

CaCo-2 is a human colonic carcinoma cell line which becomes differentiated in culture to form a polarized epithelium exhibiting several of the functional characteristics of native colonic tissue. In the present study, CaCo-2 cells have been used for a patch-clamp study of colonic ion conductance pathways. A large, 120 pS K(+)-selective channel was found in cells forming subconfluent monolayers in culture. Unlike Maxi-K+ channels found in other epithelial cells, this channel was not activated with elevations in cytosolic Ca2+. Channel activity was stimulated with membrane depolarization and most markedly with membrane stretch. The application of negative pressure (20 mm-Hg) to both cell-attached and excised, inside-out membrane patches caused a burst of channel activity which disappeared within seconds of suction removal. Single-channel conductance of the pressure-activated channel was decreased when quinine (100 microM) was present in the patch pipette.