Cysteinyl leukotrienes (LTC,, LTD,, and LTE,) are a class of biologically active lipids that exert potent effects on the heart. To assess their roles, we investigated the distribution of their receptors, CysLT(1) and CysLT(2), in the cardiovascular system. CysLT(2) mRNA was detected at high levels in the human atrium and ventricle and at intermediate levels in the coronary artery, whereas CysLT(2) mRNA was barely detected. Further analysis by in situ hybridization revealed that CysLT(2) mRNA was expressed in myocytes, fibroblasts, and vascular smooth muscle cells, but not in endothelial cells. When human coronary smooth muscle cells were stimulated with LTC,, the intracellular calcium concentration increased in a dose-dependent manner, and this action was partially inhibited by nicardipine. Additionally, these cells showed chemotactic responses to LTC4. This is the first report on the physiological role of CysLT(2), and the findings suggest that CysLT(2) has biological significance in the cardiovascular system.