Kinetic analysis of L-glutamine transport into porcine jejunal enterocyte brush-border membrane vesicles.
L-Glutamine transport into porcine jejunal enterocyte brush border membrane vesicles was studied. Uptake was mediated by a Na(+)-dependent and a Na(+)-independent pathway as well as by diffusion. The initial rates of glutamine uptake over a range of concentrations is both Na(+)-gradient and Na(+)-free conditions were analyzed and kinetic parameters were obtained. Na(+)-dependent glutamine transport had a K(m) of 0.77 +/- 0.16 mM and a Jmax of 70.7 +/- 5.8 pmol mg protein-1 s-1; Na(+)-independent glutamine transport had a K(m) of 3.55 +/- 0.78 mM and a Jmax of 55.1 +/- 6.6 pmol mg protein-1 s-1. The non-saturable component measured with HgCl2-poisoned brush border membrane vesicles in the Na(+)-free condition contained passive diffusion and non-specific membrane binding and was defined to be apparent glutamine diffusion and the glutamine permeability coefficient (Kdiff) was estimated to be Kdiff = 3.78 +/- 0.06 pmol 1 mg protein-1 mmol-1 s-1. Results of inhibition experiments showed that Na(+)-dependent glutamine uptake occurred primarily through the brush border system-B degree transporters, whereas Na(+)-independent glutamine uptake occurred via the system-L transporters. Furthermore, the kinetics of L-leucine and L-cysteine inhibition of L-glutamine uptake demonstrated that neutral amino acids sharing the same brush border transporters can effectively inhibit each other in their transport.
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
M Z
MZ
Fan
O
O
Adeola
M I
MI
McBurney
C I
CI
Cheeseman
D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D003545:Cysteine / Q000493:pharmacokinetics; D005973:Glutamine / Q000493:pharmacokinetics*; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology*; D007583:Jejunum / Q000166:cytology* / Q000378:metabolism*; D007700:Kinetics; D007930:Leucine / Q000493:pharmacokinetics; D008871:Microvilli / Q000378:metabolism; D012964:Sodium / Q000493:pharmacokinetics; D013552:Swine; D014316:Tritium
D005973:Glutamine; D014316:Tritium; D012964:Sodium; D007930:Leucine; D003545:Cysteine