Regulation of calcium influx by second messengers in rat mast cells.

Biphasic increases in the free intracellular calcium concentration, consisting of a large initial transient followed by a sustained elevation, are frequently observed in non-excitable cells following stimulation. In rat peritoneal mast cells a cAMP- and Ca-activated chloride current can interact with IP3-dependent calcium influx to provide the sustained elevation of intracellular Ca concentration following transient IP3-induced release of calcium from intracellular stores. This novel combination of second messenger systems provides a flexible means to modulate calcium-dependent processes such as exocytosis.