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.
Fan
M Z
MZ
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
Adeola
O
O
McBurney
M I
MI
Cheeseman
C I
CI
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