A model of calcium regulation in smooth muscle cell

A model of smooth muscle cell is proposed to describe the mechanisms by which intracellular calcium (Ca i) is regulated when the cell is stimulated by noradrenaline (NA)/agonist (Ag) or depolarized. The intracellular Ca 2+ store is comprised of two calcium pools: A-store which is sensitive to inositol 1,4,5 trisphosphate (IP 3) and C-store, insensitive to IP 3 but sensitive to Ca i. The A-store is refilled by Ca 2+ from C-store and reuptake of Ca i. The uptake rate is dependent on the degree of filling in the A-store. The C-store, activated by Ca i, is replenished by extracellular Ca 2+ (Ca 0). IP 3 generated by NA or Ag changes the A-store permeability, discharging its Ca 2+ into the cytosol. Depolarization activates Ca 2+ current through the L-type channels. The following events are simulated and compared with experimental observations: (a) Ca i transient stimulated by high K +; (b) Ca i transient and Ca 2+ efflux induced by shortlasting and longlasting NA in the absence of Ca 0; (c) effect of lanthanum on NA-induced Ca i and Ca 2+ efflux; and (d) effects of nifedipine, ryanodine, BAY K 8644 and cyclopiazonic acid on Ca i.