Objective To investigate the effect of different concentrations of endothelin on intracellular calcium level in cultured human pericardial mesothelial cells. Methods Pericardial mesothelial cells from patients undergoing open heart surgery were cultured in vitro. Cells of passage 8-10 were used in this experiment. When confluence was reached, the mesothelial cells were loaded with Fluo3/AM. The intracellular calcium concentrations in theses cultured cells were determined by confocal laser scanning microscopy after 10SUP>-7/SUP>mol/L, 10SUP>-8/SUP>mol/L, 10SUP>-9/SUP>mol/L ET being added respectively. Results Calcium concentrations in cultured mesothelial cells increased remarkably after adding three kinds of ET concentration(EM>P/EM><0.001). There was interaction between endothelin concentration and observation time (P<0.001). Conclusion Calcium in cultured mesothelial cells changed distinctly after the stimulation of different concentration of ET; Human pericardial mesothelial cells may possess important biological activity and endothelin may play an important role in the pericardium in an autocrine and/or paracrin