LTB4R is the receptor for extracellular ATP > UTP and ADP. The activity of this receptor is mediated by G proteins which activate a phosphatidylinositol-calcium second messenger system. LTB4R may be the cardiac P2Y receptor involved in the regulation of cardiac muscle contraction through modulation of L-type calcium currents. LTB4R is a receptor for leukotriene B4, a potent chemoattractant involved in inflammation and immune response.