Effects of AlF₄ ^– and ATP on intracellular calcium dynamics of crypt epithelial cells in mouse small intestine

Abstract.

Previous digital imaging analysis of intracellular calcium ion ([Ca²⁺]_i) dynamics in the crypt of the small intestine showed little response by most columnar cells to cholinergic and adrenergic agonists. The objective of the present study was to demonstrate whether G-protein activators and other transmitters elicit [Ca²⁺]_i changes in crypt cells. We used digital imaging to analyze spatiotemporal dynamics of [Ca²⁺]_i in Fura-2/AM-loaded isolated crypts of mouse duodenum and ileum. AlF₄ ^– increased [Ca²⁺]_i in crypt columnar cells. In many cases, we observed [Ca²⁺]_i oscillations, which were synchronized throughout the entire crypt. The oscillations were blocked by octanol. ATP, but not adenosine, caused a [Ca²⁺]_i increase in middle crypt-regions of the duodenum and upper regions of the ileum, and the [Ca²⁺]_i wave propagated towards the crypt bottom. The ATP-induced [Ca²⁺]_i increase was prevented by pretreatment with thapsigargin or suramin, but not by La³⁺ or an extracellular Ca²⁺-free environment. Neither dopamine, 5-hydroxytryptamine (5-HT), histamine, vasoactive intestinal peptide, substance P, cholera toxin, nor guanylin had significant effects. The [Ca²⁺]_i dynamics of Paneth cells were independent of the AlF₄ ^–-induced synchronous oscillations of columnar cells and of the ATP-induced [Ca²⁺]_i wave. In conclusion, crypt columnar cells have [Ca²⁺]_i-dependent intracellular signaling mechanisms that are linked with G proteins, and by which the cells communicate with each other. ATP elicited [Ca²⁺]_i mobilization from columnar cells via P2 receptors, although some regional differences were noted between the duodenum and ileum.