Inositol Trisphosphate Mobilizes Intracellular Calcium in Permeabilized Adrenal

Abstract: Using permeabilized chromaffin cells and the fluorescent probe Quin 2 (an indicator of free Ca?'), we found that inositol trisphosphate (IP,) specifically trig-gered an immediate and dose-dependent release of Ca2+ from intracellular stores. Desensitization of the response was observed at nonsaturating concentrations of inositol trisphosphate and resequestration of Ca2+ was not ob-served. While representing only a small fraction of the total cellular Ca2+, the amount released by IP, could sig-nificantly raise cytosolic Caz ' and may account for mus-carinic effects on Ca2+ metabolism in chromaffin cells. Key Words: Inositol trisphosphate-Intracellular cal-cium-Chromaftin cells-Quin 2. Stwhr S. J. et al. Ino-sitol trisphosphate mobilizes intracellular calcium in per-meabilized adrenal chromaffin cells. J. Neurochem. 46