Inositol trisphosphate mobilizes intracellular calcium in permeabilized adrenal chromaffin cells

Using permeabilized chromaffin cells and the fluorescent probe Quin 2 (an indicator of free Ca2+), we found that inositol trisphosphate (IP3) specifically triggered 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 observed. While representing only a small fraction of the total cellular Ca2+, the amount released by IP3 could significantly raise cytosolic Ca2+ and may account for muscarinic effects on Ca2+ metabolism in chromaffin cells.