Ca2+-dependent and -independent Cl- secretion stimulated by the nitric oxide donor, GEA 3162, in rat colonic epithelium

The lipophilic nitric oxide-liberating drug, 1,2,3,4-oxatriazolium, 5-amino-3-(3,4-dichlorophenyl)-chloride (GEA 3162), concentration-dependently induced a Cl- secretion in rat colon. At a low concentration (5 x 10(-5) M), the action was Ca2+-dependent, whereas at a high concentration (5 x 10(-4) M), the response was independent from extracellular Ca2+. Fura-2 experiments at isolated colonic crypts revealed that GEA 3162 induced an increase of the cytoplasmic Ca2+ concentration due to an influx of extracellular Ca2+, probably mediated by an activation of a nonselective cation conductance as demonstrated by whole-cell patch-clamp studies. After depolarization of the basolateral membrane, GEA 3162 (5 x 10(-4) M) stimulated a cur-rent, which was suppressed by glibenclamide but was resistant against blockade of protein kinases by staurosporine, suggesting an activation of apical Cl- channels directly by the nitric oxide (NO) donor. After permeabilizing the apical membrane with the ionophore, nystatin, GEA 3162 (5 x 10(-4) M) activated basolateral K+ conductances and the Na+-K+-ATPase. Thus, the lipophilic NO donor GEA 3162 stimulates a Cl- secretion in a Ca2+-dependent and -independent manner. (C) 2002 Elsevier Science B.V. All rights reserved.