Morphological and functional analysis of protease-activated receptor 2 on intracellular calcium dynamics in rat parotid gland acinar cells

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Protease-activated receptors(PARs) represent a novel class seven transmembrane domain G-protein coupled receptors, which are activated by proteolytic cleavage. Recent studies have reported that PARs are present in a variety of cells and have been prominently implicated in the regulation of a number of vital functions. The issue of whether the stimulation of PARs induces responses in parotid glands was examined ; with special reference to intracellular Ca^<2+>([Ca^<2+>]_i) dynamics during PARs stimulation. In the present study, PAR2 mRNA was expressed strongly in the parotid glands. In parotid acinar cells, PAR2-activating peptide(PAR2-AP), SLIGRL-NH_2, induced an increase in[Ca^<2+>]_i. Both removing of extracellular Ca^<2+> and using of Ca^<2+> channel blockers did not inhibit the PAR2-AP-induced[Ca^<2+>]_i increase. The response to PAR-2 activation was mainly caused by Ca^<2+> mobilization from intracellular Ca^<2+> stores. This peptide induced Ca^<2+> release and entry were partially inhibited by the nitric oxide synthase(NOS) inhibitor, L-NAME. The NO donor, GEA 3162, but not 8-bromo-cGMP, mimicked the effects of PAR2 in activating non capacitative calcium entry(NCCE). Both KN93(a CAM kinase II inhibitor) and W7(a calmodulin inhibitor) completely blocked a Ca^<2+> release from intracellular Ca2+store and a Ca^<2+> influx from extracellular spaces. Tetracaine and DHAB partially blocked these increases. These results indicate that PAR2-AP activates NCCE pathway. And we proposed that an effect of PAR-2 in parotid gland is dependent on CAMKII and a PAR2-AP activates the ryanodine-like receptors.