Heterogeneity of pig intestinal D-glucose transport systems.
Heterogeneity of intestinal D-glucose transport is demonstrated using pig jejunal brush-border membrane vesicles in the presence of 100/0 (out/in) mM gradients each of NaCl, NaSCN, and KSCN. Two D-glucose transport systems are kinetically distinguished: high-affinity, low-capacity system 1, which is equivalent to the symporter SGLT1; and low-affinity, high-capacity system 2, which is not a member of the SGLT family but is a D-glucose and D-mannose transporter exhibiting no preference for Na(+) over K(+). A nonsaturable D-glucose uptake component has also been detected; uptake of this component takes place at rates 10 times the rate of components characterizing the classical diffusion marker L-glucose. It is also shown that, in this kinetic work, 1) use of D-glucose-contaminated D-sorbitol as an osmotic replacement cannot cause the spurious appearance of nonexistent transport systems and 2) a large range (>/=50 mM) of substrate concentrations is required to correctly fit substrate saturation curves to distinguish between low-affinity transport systems and physical diffusion.
Halaihel
N
N
Institut National de la Santé et de la Recherche Médicale, Unité 510, Faculté de Pharmacie, Université de Paris XI, 92296 Châtenay-Malabry, France.
Gerbaud
D
D
Vasseur
M
M
Alvarado
F
F
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D004396:Coloring Agents / Q000494:pharmacology; D004058:Diffusion; D005947:Glucose / Q000493:pharmacokinetics*; D007408:Intestinal Absorption / Q000502:physiology*; D007413:Intestinal Mucosa / Q000737:chemistry / Q000378:metabolism; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008358:Mannose / Q000493:pharmacokinetics; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009995:Osmosis / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology; D051269:Sodium-Glucose Transporter 1; D013012:Sorbitol / Q000493:pharmacokinetics; D013552:Swine; D013861:Thiocyanates / Q000494:pharmacology
D004396:Coloring Agents; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D051269:Sodium-Glucose Transporter 1; D013861:Thiocyanates; D012965:Sodium Chloride; D013012:Sorbitol; C024553:sodium thiocyanate; D005947:Glucose; D008358:Mannose; C009941:potassium thiocyanate