Regulation of cytosolic Ca2+ is important for a variety of cell functions. The ryanodine receptor (RyR) is a Ca2+ channel that conducts Ca2+ from internal pools to the cytoplasm. To demonstrate the presence of the RyR in the pancreatic acinar cell, we performed reverse transcriptase (RT)-PCR, Western blot, immunocytochemistry and microscopic Ca2+-release measurements on these cells. RT-PCR showed the presence of mRNA for RyR isoforms 1, 2 and 3 in both rat pancreas and dispersed pancreatic acini. Furthermore, mRNA expression for RyR isoforms 1 and 2 was demonstrated by RT-PCR in individual pancreatic acinar cells selected under the microscope. Western-blot analysis of acinar cell immunoprecipitates, using antibodies against RyR1 and RyR2, showed a high-molecular-mass (> 250kDa) protein band that was much less intense when immunoprecipitated in the presence of RyR peptide. Functionally, permeablized acinar cells stimulated with the RyR activator, palmitoyl-CoA, released Ca2+ from both basolateral and apical regions. These data show that pancreatic acinar cells express multiple isoforms of the RyR and that there are functional receptors throughout the cell.
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Fitzsimmons et al. (2000) studied this question.