INDEPENDENT MODES OF PROPAGATION OF CALCIUM WAVES IN SMOOTH-MUSCLE CELLS

The purinergic agonist adenosine triphosphate (ATP) stimulates an init ial transient followed by subsequent oscillations in cytosolic calcium ion concentration ([Ca2+]i) in individual porcine aortic smooth muscl e cells. Using microinjection of fura-2 covalently coupled to dextran, we have analyzed in detail the spatial and temporal features of the o scillations. We have observed both cytoplasmic calcium waves and gradi ents within single cells. Single cells can contain multiple loci of in itiation of oscillations. Independent oscillations in a single cell ca n have independent frequencies and these oscillations can propagate wi thout interference across the same region of the cell, suggesting that they arise either from separately regulated stores of Ca2+ or a singl e Ca2+ store operated by two separate release mechanisms. The shape of the wave front and the manner of the wave's decay can vary from one o scillation to the next. Ca2+ signaling in individual arterial smooth m uscle cells thus displays complex spatial and temporal organization.