[Mechanisms of mobilization of intracellular stored calcium]

The release of intracellular stored Ca2+ is mainly regulated by an inositol 1,4,5-triphosphate (IP3) receptor system and a ryanodine receptor system. The former induces Ca2+ release directly when the receptors are bound to IP3. The later may function through the Ca2+ induced Ca2+ release mechanism when the ryanodine receptors are activated. Cyclic ADP ribose, a metabolite of NAD+ which is regulated by complicated mechanisms, is one of the most important factors causing activation of ryanodine receptors. The two systems may interact with each other to regulate Ca2+ release from intracellular calcium pool.