Substrate specificity of the rat liver Na(+)-bile salt cotransporter in Xenopus laevis oocytes and in CHO cells
| Autor: | Bruno Hagenbuch, Alice Schroeder, Uta Eckhardt, Peter J. Meier, Claudio D. Schteingart, Alan F. Hofmann, Ronald E. Tynes, Bruno Stieger |
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| Rok vydání: | 1998 |
| Předmět: |
Taurocholic Acid
Organic anion transporter 1 Physiology Estrone Sodium chemistry.chemical_element Organic Anion Transporters Sodium-Dependent CHO Cells Substrate Specificity chemistry.chemical_compound Xenopus laevis Physiology (medical) Cricetinae medicine Animals Hepatology biology Symporters Chinese hamster ovary cell Gastroenterology Sodium butyrate Rats chemistry Biochemistry Liver Symporter biology.protein Oocytes Cotransporter Carrier Proteins Bumetanide medicine.drug |
| Zdroj: | The American journal of physiology. 274(2) |
| ISSN: | 0002-9513 |
| Popis: | It has been proposed that the hepatocellular Na+-dependent bile salt uptake system exhibits a broad substrate specificity in intact hepatocytes. In contrast, recent expression studies in mammalian cell lines have suggested that the cloned rat liver Na+-taurocholate cotransporting polypeptide (Ntcp) may transport only taurocholate. To characterize its substrate specificity Ntcp was stably transfected into Chinese hamster ovary (CHO) cells. These cells exhibited saturable Na+-dependent uptake of [3H]taurocholate [Michaelis constant ( Km) of ∼34 μM] that was strongly inhibited by all major bile salts, estrone 3-sulfate, bumetanide, and cyclosporin A. Ntcp cRNA-injected Xenopus laevis oocytes and the transfected CHO cells exhibited saturable Na+-dependent uptake of [3H]taurochenodeoxycholate ( Kmof ∼5 μM), [3H]tauroursodeoxycholate ( Kmof ∼14 μM), and [14C]glycocholate ( Kmof ∼27 μM). After induction of gene expression by sodium butyrate, Na+-dependent transport of [3H]estrone 3-sulfate ( Kmof ∼27 μM) could also be detected in the transfected CHO cells. However, there was no detectable Na+-dependent uptake of [3H]bumetanide or [3H]cyclosporin A. These results show that the cloned Ntcp can mediate Na+-dependent uptake of all physiological bile salts as well as of the steroid conjugate estrone 3-sulfate. Hence, Ntcp is a multispecific transporter with preference for bile salts and other anionic steroidal compounds. |
| Databáze: | OpenAIRE |
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