Figure 2

Cells were exposed to 1 mM ATP in the presence and the absence of extracellular calcium. The resulting increase in the cytoplasmic Ca²⁺-concentration was quantified using fluorescence microscopy. For each cell line, the Ca²⁺-increase with external calcium was set to 100% (black columns) and the Ca²⁺-increase without external calcium (white columns) was expressed as percent of the increase with external calcium. In normal bronchial epithelial (NHBE), Small Cell Lung Cancer (H1339) and Adeno-Carcinoma (HCC) cells, the ATP-induced Ca²⁺-increase was independent of the presence of extracellular calcium suggesting a minor role for Ca²⁺-influx. In Squamous Cell Lung Carcinoma (EPLC) and Large Cell Lung Carcinoma (LCLC) cells, the ATP-induced Ca²⁺-increase was lower in the absence of extracellular calcium (n = 42 – 162 cells, * = P < 0.001 versus "with external calcium").