Volume 117, Issue 3, Pages 688-695 (September 1999) Localization and function of the organic anion–transporting polypeptide Oatp2 in rat liver  Christoph Reichel, Bo Gao, Jessica van Montfoort, Valentino Cattori, Christoph Rahner, Bruno Hagenbuch, Bruno Stieger, Toshinori Kamisako, Peter J. Meier  Gastroenterology  Volume 117, Issue 3, Pages 688-695 (September 1999) DOI: 10.1016/S0016-5085(99)70463-4 Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 1 Specificity of the Oatp1 and Oatp2 antibodies. Antibodies against the C-terminal ends of Oatp1 and Oatp2 were raised in rabbits and used for Western blotting of basolateral liver plasma membrane proteins as described in Materials and Methods. Initial SDS–polyacrylamide gel electrophoresis was performed with 100 μg of basolateral liver plasma membrane protein in each lane. The differences in the mean molecular mass of Oatp1 and Oatp2 indicate the specificity of the antisera used. Gastroenterology 1999 117, 688-695DOI: (10.1016/S0016-5085(99)70463-4) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 2 Distribution of Oatp2 mRNA in intact rat liver. In situ hybridization was performed as described in Materials and Methods by using Oatp2 (A) antisense and (B) sense riboprobes. (A) Acinar distribution of Oatp2-mRNA (c, central hepatic vein; p, periportal area). (B) No specific signal was obtained with the sense riboprobe. Gastroenterology 1999 117, 688-695DOI: (10.1016/S0016-5085(99)70463-4) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 3 Immunolocalization of Oatp1 and Oatp2 in intact rat liver. Semithin cryosections of rat liver were probed with the antisera against Oatp1 and Oatp2. Labeling was visualized with a green fluorescent secondary antibody. Bile canaliculi are visualized with a monoclonal antibody against aminopeptidase N (red fluorescence). (A) Overview showing homogeneous basolateral expression of Oatp1 throughout the hepatic lobule. (B) Overview showing compartmentalized basolateral expression of Oatp2 in midzonal to perivenous hepatocytes. (C and D) Higher-magnification views of Oatp2 expression in the (C) periportal and (D) perivenous areas. CV, central vein. PV, portal vein. Gastroenterology 1999 117, 688-695DOI: (10.1016/S0016-5085(99)70463-4) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 4 Kinetics of (A) Oatp1- and (B) Oatp2-mediated BQ-123 uptake in cRNA-injected X. laevis oocytes. Oocytes were injected with 5 ng of Oatp1 and Oatp2 cRNAs or with an equal volume of water. They were cultured for 2.5 days at 18°C and then incubated with increasing concentrations of labeled [3H]BQ-123 and unlabeled BQ-123 in a sodium-free choline chloride medium (see Materials and Methods). Uptake measurements were performed at 30 minutes because separate experiments showed linear BQ-123 uptake up to 45 minutes. Unspecific uptake into water-injected oocytes (<10% of total uptake in cRNA-injected oocytes) was substracted from all uptake measurements. Results are given as means ± SD of 10–15 uptake measurements. Kinetic analysis was performed by using a computer-based nonlinear regression analysis of the initial uptake values. Gastroenterology 1999 117, 688-695DOI: (10.1016/S0016-5085(99)70463-4) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 5 Comparison of various substrate transport values in Oatp1 and Oatp2 cRNA–injected X. laevis oocytes. Oocytes were injected with 1 ng of Oatp1 cRNA, 5 ng of Oatp2 cRNA, or the same volume of cRNA-free water. Uptakes of sulfo-[3H]lithotaurocholate (20 μmol/L) and [35S]BSP (4 μmol/L) were determined at 15 minutes and of [3H]BMG (0.1 μmol/L) at 30 minutes in a sodium-free choline chloride medium (see Materials and Methods). All uptake values are given as means ± SD of 10–15 uptake measurements. Gastroenterology 1999 117, 688-695DOI: (10.1016/S0016-5085(99)70463-4) Copyright © 1999 American Gastroenterological Association Terms and Conditions