Intracellular free calcium concentration and cisplatin resistance in humanlung adenocarcinoma A(549) cells

Human lung adenocarcinoma A(549) cells sensitive and A(549)/DDP cells resis tant to Cis-dichlorodiammine platinum[II] (cisplatin) exhibit different int racellular free calcium and calcium fluorescence images labeled with Fura-2 /AM and Fluo-3/AM as judged by dual-excitation fluorescence assay, Miracal Imaging and Laser Scanning Confocal Microscopy (LSCM) of single cells. The concentration of intracellular free calcium of the resistant A549/DDP cells is one third that of the sensitive A(549) cells. The efflux of Rhodamine 1 23 in resistant A(549)/DDP cells is faster than that in sensitive A(549) ce lls. Tn addition, A(549)/DDP cells have an increase of Phosphatidylinositol 4-kinase (PtdIns 4-kinase) activity in the plasma membrane. So it is tenta tively suggested that the increase in PtIns 4-kinase activity resulting fro m lower intracellular Ca2+ concentration leads to an increase of its enzyma tic products-PIP and PIP2, which may stimulate the activity of P-glycoprote in.