When incubated in the presence of Na+ ions, dissected rat incisor odontoblasts extruded Ca2+ ions, as detected by tetracycline fluorimetry. Also odontoblast mitochondria, obtained by subcellular fractionation and monitored by ion-specific mini-electrode technique, were found to extrude Ca2+ upon addition of Na+ ions. These findings demonstrate the presence of Na+/Ca2+ antiports in the odontoblast plasma membrane as well as in the odontoblast mitochondrial inner membrane. In addition, evidence was found for an ATP-dependent Ca2+ ion extrusion across the plasma membrane in these cells.