Apical adenosine activates an amiloride-sensitive conductance in human intestinal cell line HT29cl.19A

We studied the effects of stimulation of the apical adenosine receptor on ion transport by HT29cl.19A cells with the conventional microelectrode technique. Adenosine (100 mu M) caused an increase in the transepithelial potential (3.6 +/- 0.4 mV) and equivalent short-circuit current (I-sc, 21 +/- 3 mu A/cm(2)), a transient depolarization of the apical membrane potential (14 +/- 2 mV), and a decrease in the apical membrane resistance. The increase in I-sc was additive to the effect of forskolin or basolateral addition of a maximal concentration of adenosine. Bumetanide, applied after adenosine, caused a further depolarization (7 +/- 2 mV) concomitant with a decrease in I-sc (-13 +/- 2 mu A/cm(2)) and an increase in the basolateral membrane resistance. Substitution of Cl- with gluconate or Na+ with N-methylglucamine reduced the response to adenosine by >60%. The response was also reduced by a low concentration of amiloride. We conclude that stimulation of the apical adenosine receptor activated a cation conductance in the apical membrane.