Calcium ionophore plus excision induce a large conductance chloride channel in membrane patches of human colon carcinoma cells HT-29cl.19A.
In excised inside-out membrane patches of the human colon carcinoma HT-29cl.19A cells a large conductance (373 +/- 10 pS) chloride channel was found. Channel activity could only be observed after excision of patches from cells incubated with calcium ionophore. The channel was never observed in cell-attached patches. The channel was strongly voltage dependent, being open only between +30 and -30 mV clamp potentials. The selectivity sequence among anions, deduced from reversal potentials, was I > Br > Cl > F > gluconate. The PNa/PCl was 0.09. Although a similar type of channel has been described earlier, this is the first report stating its appearance in patches of intestinal epithelial cells requiring the combined action of Ca2+ ionophore and excision, suggesting its control by an intracellular compound.
Department of Experimental Zoology, University of Amsterdam, The Netherlands.
R B
RB
Bajnath
J A
JA
Groot
H R
HR
de Jonge
M
M
Kansen
J
J
Bijman
D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D018118:Chloride Channels; D003110:Colonic Neoplasms / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000187:drug effects* / Q000502:physiology; D014407:Tumor Cells, Cultured
D018118:Chloride Channels; D008565:Membrane Proteins; D000001:Calcimycin; D002118:Calcium