Calcium signaling induced by angiotensin II in the pancreatic acinar cell line AR42J

The purpose of this study was to characterize the nature and mechanisms of angiotensin II-evoked calcium signaling in AR42J cells. Cytosolic calcium c oncentrations were determined using fura-2-based microfluorimetry. Angioten sin II causes elevations in free cytosolic calcium ([Ca2+](i)) in the rat p ancreatic acinar cell line AR42J, The mechanisms of angiotensin II-evoked c alcium signaling were examined using fura-2-based fluorescent digital micro scopy. Angiotensin II caused dose-dependent increments in [Ca2+](i) over a concentration range of 0.1-1,000 nM, with an average increment of 243 +/- 1 6 nM at an angiotensin II concentration of 1,000 nM. Dup753, an AT(1)-speci fic antagonist, inhibited angiotensin II-evoked signaling, whereas the AT(2 ) antagonist PD123,319 had no effect. Preincubation with the phospholipase C inhibitor U73122 reduced the response in [Ca2+](i) to 25% of that of the control. Thapsigargin abolished angiotensin II-evoked calcium signaling. Th e inositol 1,4,5-trisphosphate receptor antagonist heparin introduced by ra diofrequency electroporation inhibited responses to 46 +/- 6% of controls. Angiotensin II-evoked signals were reduced in magnitude and duration by eli mination of Ca2+ from the extracellular buffer. Preincubation with pertussi s toxin (100 ng/ml) had no effect. Angiotensin II did not stimulate cyclic AMP or suppress vasoactive intestinal peptide stimulated cyclic AMP product ion over the concentration range that caused Ca2+ signaling.