Na-dependent D-glucose transport by intestinal brush border membrane vesicles from gilthead sea bream (Sparus aurata).
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 MgCl(2) 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, alpha-methyl-D-glucose, 3-O-methyl-D-glucose and 2-deoxy-D-glucose, and showed stereospecificity. Apparent affinity constants of D-glucose transport (K(t)) 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.
Sala-Rabanal
M
M
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.
Gallardo
M A
MA
Sánchez
J
J
Planas
J M
JM
D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D007422:Intestines / Q000502:physiology*; D008871:Microvilli / Q000378:metabolism*; D021541:Sea Bream / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose