PREDOMINANT CONTRIBUTION OF ORGANIC ANION TRANSPORTING POLYPEPTIDE OATP-B (OATP2B1) TO APICAL UPTAKE OF ESTRONE-3-SULFATE BY HUMAN INTESTINAL CACO-2 CELLS

• DOI: 10.1124/dmd.106.009530
• Publication Date: 2006-05-20T00:43:33Z
• Authors: Yoshimichi Sai; Yosuke Kaneko; Satsuki Ito; Keisuke Mitsuoka; Yukio Kato; Ikumi Tamai; Per Artursson; Akira Tsuji
• Keywords: Estrone sulfate; Organic anion-transporting polypeptide; Caco-2; HEK 293 cells; Apical membrane; Organic anion

Human organic anion transporting polypeptide OATP-B (OATP2B1) is a pH-sensitive transporter expressed in the apical membranes of small intestinal epithelial cells. In this study, we have examined contribution to uptake [³H]estrone-3-sulfate Caco-2 cells comparison with those its homologs OATP-D (OATP3A1) and OATP-E (OATP4A1). Immunocytochemical study revealed that The by was Na⁺-independent inhibited several anions. It showed biphasic saturation kinetics <i>K</i>_m values 1.81 μM 1.40 mM. human embryonic kidney (HEK) 293 stably expressing (HEK293/OATP-B) also value for estrone-3-sulfate (1.56 μM) close high-affinity component observed mRNA expression level higher than or jejunum biopsies from healthy volunteers. normalized were similar HEK293/OATP-B specific activity per much OATP-E. [³H]Estrone-3-sulfate membrane vesicles prepared exhibited an overshoot phenomenon presence inwardly directed H⁺ gradient, suggesting gradient driving force transport OATP-B. These results suggest predominantly responsible