Glutamine transport by human intestinal basolateral membrane vesicle.
This study characterizes for the first time, by use of a well-validated technique, glutamine transport across human basolateral membrane vesicles. Glutamine transport represented uptake into an osmotically active intravesicular space without significant metabolism. Glutamine uptake was temperature- and pH-dependent with maximal uptake at pH 7.5, and it was mediated by sodium-dependent and -independent processes. The initial rate of uptake was linear up to 20 s, as depicted by the formula gamma (nmol/mg protein) = 0.0009 X (s) - 0.0011 (r = 0.99). Kinetic analysis of glutamine uptake at concentrations between 0.01 and 0.3 mmol/L at 5 s under sodium and potassium gradients showed a maximal transport capacity (Vmax) of 0.39 +/- 0.04 and 0.21 +/- 0.02 nmol.mg protein-1.5 s-1 for sodium-dependent and -independent processes, respectively (p less than 0.01). Km values were 0.17 +/- 0.04 and 0.06 +/- 0.2 mmol/L, respectively (p less than 0.05). Glutamine uptake under the sodium-gradient condition was electrogenic whereas under the potassium-gradient it was electroneutral. Neutral amino acids inhibited both sodium-dependent and -independent processes. This study confirms and characterizes the presence of carrier-mediated glutamine uptake at the basolateral membranes of human enterocytes.
Ghishan
F K
FK
Department of Pediatrics, Vanderbilt University, Nashville, TN.
Arab
N
N
Bulus
N
N
Said
H
H
Pietsch
J
J
Abumrad
N
N
D001485:Basement Membrane / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D005973:Glutamine / Q000378:metabolism* / Q000493:pharmacokinetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism; D009994:Osmolar Concentration; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013696:Temperature
D005973:Glutamine; D012964:Sodium; D011188:Potassium