In Western blot analyses the monoclonal antibody mESL reacts selectively with the 90 kD protein (after SDS-PAGE) present in the basolateral membrane fractions of human liver. According to a recent new nomenclature this hepatocyte-specific protein is identical to OATP1B1 (Hagenbuch and Meier, 2003) also known as OATP-C. Using immunofluorescence microscopy mESL stains the sinusoidal (basolateral) membranes in frozen sections of human liver, hepatocellular carcinoma and the human cell line HEK293 transfected with SLC21A6. Polypeptide reacting: OATP2/OATP1B1, human organic anion transporter SLC21A6 (90 kD). Reactivity on cultured cell lines: SCL21A6 transfected HEK293 cells; negative with HepG2 and PLC. Hagenbuch E, Meier PJ: The superfamily of organic anion transporting polypeptides. Biochim Biophys Acta 1609, 1-18 (2003)