Na-dependent <Emphasis Type="SmallCaps">D</Emphasis>-Glucose Transport by Intestinal Brush Border Membrane Vesicles from Gilthead Sea Bream (<Emphasis Type="Italic">Sparus aurata</Emphasis>) |
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Authors: | M?Sala-Rabanal Email author" target="_blank">MA?GallardoEmail author J?Sánchez JM?Planas |
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Institution: | (1) Departament de Fisiologia (Centre de Referència i Desenvolupament en Aqüicultura de la Generalitat de Catalunya), Facultat de Biologia, Universitat de Barcelona, Diagonal 645, Barcelona, E-08028, Spain;(2) Departament de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona, Joan XXIII s/n, Barcelona, E-08028, Spain |
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Abstract: | Brush border membrane vesicles (BBMV) enriched in sucrase, maltase and alkaline phosphatase, and impoverished in Na+-K+-ATPase, were isolated from proximal and distal intestine of the gilthead sea bream (Sparus aurata) by a MgCl2 precipitation method. Vesicles were suitable for the study of the characteristics of D-glucose apical transport. Only one D-glucose carrier was found in vesicles from each intestinal segment. In both cases, the D-glucose transport system was sodium-dependent, phlorizin-sensitive, significantly inhibited by D-glucose, D-galactose, α-methyl-D-glucose, 3-O-methyl-D-glucose and 2-deoxy-D-glucose, and showed stereospecificity. Apparent affinity constants of D-glucose transport (Kt) were 0.24 ± 0.03 mM in proximal and 0.18 ± 0.03 mM in distal intestine. Maximal rate of influx (Jmax) was 47.3 ± 2.2 pmols. mg−1 protein for proximal and 27.3 ± 3.6 pmols. mg−1 protein for distal intestine. Specific phlorizin binding and relative abundance of an anti-SGLT1 reactive protein were significantly higher in proximal than in distal BBMV. These results suggest the presence of the same D-glucose transporter along the intestine, with a higher density in the proximal portion. This transporter is compatible with the sodium-dependent D-glucose carrier described for other fish and with the SGLT1 of higher vertebrates.This revised version was published online in June 2005 with a corrected cover date. |
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Keywords: | SGLT1 Proximal intestine Distal intestine Brush border membrane vesicles Freezing Fish |
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