Basic ResearchHepatic uptake of cholecystokinin octapeptide by organic anion-transporting polypeptides OATP4 and OATP8 of rat and human liver☆,☆☆
Section snippets
Materials
Radiolabeled [3H]CCK-8 (69-74 Ci/mmol) was obtained from Amersham Pharmacia Biotech (Buckinghamshire, England). Collagenase type 2 CLS was from Worthington Biochemical Corp. (Freehold, NJ). All other chemicals were of the highest degree of purity available and were readily available from commercial sources.
Uptake studies in xenopus laevis oocytes
Capped Oatp/OATP complementary RNA (cRNA) was synthesized in vitro using the mMESSAGE mMACHINE T7 kit (Ambion, Austin, TX) as previously described.21X. laevis oocytes were prepared as
Results
We initially tested transport of [3H]CCK-8 by the known Oatps of rat liver. Three days after injection of cRNA into X. laevis oocytes, the liver-specific Oatp4 (Slc21a6) efficiently mediated CCK-8 transport (25-fold stimulation of uptake compared with water-injected oocytes), whereas oocytes expressing Oatp1 (Slc21a1), Oatp2 (Slc21a5), or Oatp3 (Slc21a7) did not show any measurable uptake (Figure 1A).
Discussion
Over the past 2 decades, increasing evidence has suggested carrier-mediated hepatic uptake of the gastrointestinal peptide hormone CCK-8, including (1) a concentration gradient for this hormone between the portal and the systemic venous circulation;30 (2) reduced biologic activity of CCK-8 after intraportal administration compared with systemic administration;31 (3) elevated CCK-8 plasma levels in patients with liver cirrhosis;32 (4) rapid appearance of radiolabeled CCK-8 in the liver after
Acknowledgements
The authors thank Monika Gersbach-Fey for expert technical assistance.
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Cited by (149)
Organic Anion Transporting Polypeptide (OATP) 1B3 is a Significant Transporter for Hepatic Uptake of Conjugated Bile Acids in Humans
2023, Cellular and Molecular Gastroenterology and HepatologyDrug Transport—Uptake
2022, Comprehensive PharmacologyDifferences in transport function of the human and rat orthologue of the Organic Anion Transporting Polypeptide 2B1 (OATP2B1)
2021, Drug Metabolism and PharmacokineticsCitation Excerpt :Differences in substrate recognition of closely related OATP family members are well-known. One example are the liver-enriched transporters OATP1B1 and OATP1B3, which exhibit a broad substrate overlap [46], but transport of cholecystokinin 8 (CCK-8) is a unique feature of OATP1B3 [47], while transport of E1S is only mediated by OATP1B1 [48]. Testing the influence of amino acid exchanges revealed that non-conserved amino acid residues in TMD-1, TMD-10, and the ECL-6 are relevant for CCK-8 substrate recognition [56].
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2020, Toxicology and Applied PharmacologyCitation Excerpt :However, the mechanism remains to be understood. Although CCK-8 has no metabolic impact on hepatocytes, it is efficiently taken up from the portal blood into the liver where it is rapidly metabolized and excreted (Ismair et al., 2001). Studies on the uptake of CCK-8 in Xenopus oocytes expressing four organic anion-transporting polypeptides of rat liver and of human liver as well as in primary cultured rat hepatocytes showed that CCK-8 is selectively transported by rat Oatp1b2 (Oatp4) and human OATP1B3 (OATP8), with Km values of 14.9 ± 2.9 μM and 11.1 ± 2.9 μM, respectively (Ismair et al., 2001).
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Address requests for reprints to: Gerd A. Kullak-Ublick, M.D., Division of Clinical Pharmacology and Toxicology, Department of Medicine, University Hospital, CH-8091 Zurich, Switzerland. e-mail: [email protected]; fax: (41) 1-255-4411.
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Supported by grant 32-59155.99 from the Swiss National Science Foundation, Bern, Switzerland.