The ryanodine receptor mediates intracellular Ca²⁺ mobilization in muscle and nerve, but its physiological role in nonexcitable cells is less well defined. Like adenosine 3',5'-cyclic monophosphate and inositol 1,4,5-trisphosphate, cyclic ADP-ribose (0.3-5 µM) and ADP (1-25 µM) produced a concentration-dependent rise in cytosolic Ca²⁺ in permeabilized rat parotid acinar cells. Adenosine and AMP were less effective. Ryanodine markedly depressed the Ca²⁺-mobilizing action of the adenine nucleotides and forskolin in permeabilized cells and was likewise effective in depressing the action of forskolin in intact cells. Cyclic ADP-ribose-evoked Ca²⁺ release was enhanced by calmodulin and depressed by W-7, a calmodulin inhibitor. A fluorescently labeled ligand, 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3,4-diaza-s-indacene-3-propionic acid-glycyl ryanodine, was synthesized to detect the expression and distribution of ryanodine receptors. In addition, ryanodine receptor expression was detected in rat parotid cells with a sequence highly homologous to a rat skeletal muscle type 1 and a novel brain type 1 ryanodine receptor. These findings demonstrate the presence of a ryanodine-sensitive intracellular Ca²⁺ store in rat parotid cells that shares many of the characteristics of stores in muscle and nerve and may mediate Ca²⁺-induced Ca²⁺ release or a modified form of this process.