Hepatic uptake of cholecystokinin octapeptide by organic anion-transporting polypeptides OATP4 and OATP8 of rat and human liver

doi:10.1053/gast.2001.28704

Gastroenterology

Volume 121, Issue 5, November 2001, Pages 1185-1190

https://doi.org/10.1053/gast.2001.28704 Get rights and content

Abstract

Background & Aims: Cholecystokinin (CCK) is a major gastrointestinal peptide hormone that is released postprandially from the small intestine and exerts marked effects on gallbladder and gastrointestinal motility. The smaller isoforms CCK-8 and CCK-4 are rapidly taken up into hepatocytes, metabolized, and excreted into bile. Our aim was to identify and characterize the hepatocellular CCK-8 uptake system. Methods: CCK-8 uptake was measured in Xenopus laevis oocytes expressing the organic anion-transporting polypeptides of rat liver (Oatp1, Oatp2, Oatp3, or Oatp4) and of human liver (OATP-A, OATP-B, OATP-C, or OATP8) and in primary cultured rat hepatocytes. Results: Rat Oatp4 and human OATP8 efficiently mediated CCK-8 uptake in oocytes, with Michaelis constant (K_m) values of 14.9 ± 2.9 μmol/L and 11.1 ± 2.9 μmol/L, respectively. CCK-8 uptake by hepatocytes was also saturable, with a K_m of 6.7 ± 2.1 μmol/L. The K_m value in rat hepatocytes is consistent with Oatp4-mediated transport. Conclusions: CCK-8 is selectively transported by rat Oatp4 and human OATP8, both of which are exclusively expressed at the basolateral membrane of hepatocytes. These 2 transporters are the first and probably the predominant hepatic uptake systems for CCK-8 and may be critical for the rapid clearance of this hormone from the circulation.

GASTROENTEROLOGY 2001;121:1185-1190

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).

. Comparison of CCK-8 uptake by X. laevis oocytes expressing either (A) rat Oatps or (B) human

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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^☆: 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.

^☆☆: Supported by grant 32-59155.99 from the Swiss National Science Foundation, Bern, Switzerland.

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Basic ResearchHepatic uptake of cholecystokinin octapeptide by organic anion-transporting polypeptides OATP4 and OATP8 of rat and human liver☆,☆☆

Abstract

Section snippets

Materials

Uptake studies in xenopus laevis oocytes

Results

Discussion

Acknowledgements

Gastroenterology

Gastroenterology

Gastroenterology

J Biol Chem

J Biol Chem

FEBS Lett

J Biol Chem

Hepatology

Hepatology

Regul Pept

J Biol Chem

Cholecystokinin: isolation, structure, and functions

Regulation of gastric emptying in humans by cholecystokinin

J Clin Invest

Pure cholecystokinin: pancreatic protein and bicarbonate response

Digestion

The action of gastrin and cholecystokinin-related peptides on pancreatic secretion in the rat

Q J Exp Physiol Cogn Med Sci

Choleretic effects of cholecystokinin, gastrin II, and caerulein in the dog

Am J Physiol

Cholecystokinin-pancreozymin: recent developments

Am J Dig Dis

Basic Research
Hepatic uptake of cholecystokinin octapeptide by organic anion-transporting polypeptides OATP4 and OATP8 of rat and human liver☆,☆☆