Cross talk between plasma membrane and sarcoplasmic reticulum in canine airway smooth muscle

Abstract

In smooth muscle, contractions under pharmacomechanical and electromechanical coupling mechanism control rely on mobilization of intracellular calcium and on calcium influx from the extracellular space, respectively. In airway smooth muscle, pharmacomechanical coupling seems to predominate. Even if extracellular calcium enters the cell during agonist stimulation, and contributes to the maintained plateau phase of a prolonged stimulation-induced contraction, it does not result from membrane depolarization and is not part of the electromechanical coupling mechanism. Pharmacomechanical and electromechanical coupling are most likely not independent processes: we present here an example of cross talk between plasma membrane and sarcoplasmic reticulum, which results in an almost complete switch in the E-C coupling process from pharmaco- to electromechanical mode in tracheal smooth muscle.