The monoclonal antibody against the canine Na+ -Ca2+-exchanger, recognizes two neighboring but non-overlapping sequences of the hydrophilic region of the exchanger, connecting the putative transmembrane segments 5 and 6. The antibody was evaluated for specificity and potency by immunoblotting, and immunoprecipitation (see reference). It recognizes virtually only NCX1 in monkey, horse, dog, rat, bovine and mouse tissue. At higher concentrations it reacts faintly with NCX2, whereas NCX3 is not recognized. Both splice variants with exon A (heart, nervous system) and exon B (kidney, glia) are recognized.