Multiple isoforms of the ryanodine receptor are expressed in rat pancreatic acinar cells

Regulation of cytosolic Ca2+ is important for a variety of cell functions. The ryanodine receptor (RyR) is a Ca2+ channel that conducts Ca2+ from inte rnal pools to the cytoplasm. To demonstrate the presence of the RyR in the pancreatic acinar cell, we performed reverse transcriptase (RT)-PCR, Wester n blot, immunocytochemistry and microscopic Ca2+-release measurements on th ese cells. RT-PCR showed the presence of mRNA for RyR isoforms 1, 2 and 3 i n both rat pancreas and dispersed pancreatic acini. Furthermore, mRNA expre ssion for RyR isoforms 1 and 2 was demonstrated by RT-PCR in individual pan creatic acinar cells selected under the microscope. Western-blot analysis o f acinar cell immunoprecipitates, using antibodies against RyR1 and RyR2, s howed a high-molecular-mass (> 250 kDa) protein band that was much less int ense 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 th at pancreatic acinar cells express multiple isoforms of the RyR and that th ere are functional receptors throughout the cell.