Biological and Pharmaceutical Bulletin
Online ISSN : 1347-5215
Print ISSN : 0918-6158
ISSN-L : 0918-6158
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Kinetic Characterization of Carrier-Mediated Transport Systems for D-Glucose and Taurocholate in the Everted Sacs of the Rat Colon
Shigemitsu TomeiMayumi TorimotoYayoi HayashiKatsuhisa InoueHiroaki YuasaJun Watanabe
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2003 Volume 26 Issue 6 Pages 899-901

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Abstract

The present study was aimed at kinetically characterizing the carrier-mediated transport systems for D-glucose and taurocholate in the rat colon, compared with their respective counterparts in the small intestine. The transport of these compounds was evaluated by measuring the initial uptake into everted intestinal tissue sacs. The uptake of both D-glucose and taurocholate was highly saturable, conforming to Michaelis–Menten kinetics without an appreciable nonsaturable transport component. The Michaelis constant (Km) was 0.43 and 0.021 mM, respectively, for D-glucose and taurocholate and the maximum transport rate (Jmax) was 0.82 and 0.056 nmol/min/100 mg wet tissue weight (wtw), respectively. For both compounds, these values of Km and Jmax in the colon were one to three orders of magnitude smaller than those in the small intestine, suggesting that the transport systems in the colon have by far a higher affinity and a lower transport capacity than their counterparts in the small intestine. However, it is now evident from kinetic studies that carrier-mediated transport systems for D-glucose and taurocholate are also present in the colon. It will be interesting to explore the possibility that they could be used for oral drug delivery via the colon. Their physiological roles would also be of interest.

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© 2003 The Pharmaceutical Society of Japan
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