Spatial characterisation of ryanodine-induced calcium release in mouse pancreatic acinar cells.

In pancreatic acinar cells, agonists evoke intracellular Ca(2+) transients which are initiated in the apical region of these polarized cells. There are contradictory experimental data concerning Ca(2+) release from ryanodine receptors (RyRs) in the apical region. In the present study, we have used low doses of ryanodine to open RyRs leading to the release of Ca(2+) from intracellular stores. Ryanodine causes Ca(2+) release that is initiated in the apical region of the cell but is dependent upon functional inositol 1,4,5-trisphosphate receptors (IP(3)Rs). These results suggests that co-ordinated release from co-localized RyRs and IP(3)Rs underlies the increased sensitivity of the apical region to initiation of intracellular Ca(2+) transients.