A VOLTAGE, CALCIUM, AND ATP SENSITIVE NONSELECTIVE CATION CHANNEL IN HUMAN COLONIC TUMOR-CELLS

A non selective cation channel has been identified in the human colonic cell lines T84 and HT29D4 using the patch clamp technique. The channel is equally permeable to Na+ and K+, has a linear current-voltage relationship and a conductance of about 20 pS in symmetrical NaCl conditions. The channel is not permeable to chloride or to large organic cations such as N-methyl-D-glucamine. The open probability of the channel is voltage dependent. Cytosolic Ca2+ concentrations higher than 0.1 mM are required to activate the channel. The channel is blocked by cytosolic ATP (1 mM). 3′,5-dichlorodiphenylamine-2-carboxylic acid and 5-nitro-2-(3-phenylpropylamino)-benzoic acid inhibit the channel when present on the extracellular side. The block is not voltage dependent. 3′,5-dichlorodiphenylamine-2-carboxylic acid is the most potent blocker and completely inhibits channel activity at a concentration of 50 μM. The channel is insensitive to amiloride and derivatives. © 1991.