Figure 2.

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) induce Ca²⁺ mobilization and phospholipase D (PLD) activation in type II alveolar epithelial cells. (a, c) A549 cells were labelled with 3 μm Fluo-3/AM, treated or not with EDTA, EGTA or BAPTA-AM, and further stimulated with 0·5 μm of either LPA (a) or S1P (c). The positive control consisted of A549 cells lysed with Triton X-100. Data are reported as mean ± standard deviation (SD) of triplicate values and are representative of five different experiments. (b, d) PLD activity was monitored using the Amplex Red Phospholipase D detection kit on A549 cells that were unstimulated or stimulated with 0·5 μm of either LPA (b) or S1P (d) in the presence or absence of EGTA and BAPTA-AM. The values are shown as means ± SD of triplicate values and are representative of three independent experiments. *P < 0·001 in comparison with untreated cells (data were analyzed using the unpaired Student’s t-test).