Acetylcholine induces cytosolic Ca2+ mobilization in isolated distal colonic crypts from normal and cystic fibrosis mice

In intestinal biopsies from cystic fibrosis (CF) patients acetylcholine fai ls to elicit a chloride secretion response, and this observation can be exp lained by a defect in the Ca2+ signalling pathway in CF secretory cells. We tested the hypothesis that in CF intestine, the generation of an intracell ular Ca2+ signal upon cholinergic stimulation is absent. A transgenic CF mo use model was used. Electrical measurements on intact jejunum and unstrippe d colon were performed in Ussing chambers. Intact distal colonic crypts wer e isolated, and the intracellular Ca2+ concentration was monitored using th e Ca2+-sensitive dye fura-2. Acetylcholine increased the short-circuit curr ent generated by wild-type jejunum and colon, but failed to induce a respon se in CF tissues. Acetylcholine caused a transient elevation in the intrace llular Ca2+ concentration in colonic crypts from both wild-type and CF mice ; the amplitude and timing of the response in CF crypts was indistinguishab le from that in wild-type crypts. The response to acetylcholine was also ob served in the absence of extracellular calcium, indicating intracellular st ores as the source from which the cytosolic Ca2+ concentration increased. W e conclude that the absence of a cholinergically-induced secretory response in CF intestine is not due to a defect in the generation of a Ca2+ signal in intestinal cells upon cholinergic stimulation.