title: Transport of glutamine by rat kidney brush-border membrane vesicles.
abstract: Transport of glutamine by brush-border vesicles prepared from the renal cortex was studied. The transport system had both Na+-dependent and Na+-independent components. The presence of Na+ in the incubation resulted in an 'overshoot' at 30s at which time the rates of transport were approx. 8 times the values obtained in the absence of Na+. Variation of the glutamine concentration showed that the system obeyed Michaelis-Menten kinetics with Km and Vmax. values for the Na+-dependent system of 0.86 mM and 9.6 nmol/min per mg of protein respectively. Vesicles obtained from chronically acidotic rats showed similar kinetic characteristics. The Km and Vmax. values for the Na+-dependent system were 0.76 mM and 9.6 nmol/min per mg of protein respectively. There was increased uptake of glutamine by vesicles from acidotic rats and this increase was associated with increased activity of gamma-glutamyltransferase in these preparations. Vesicles from acidotic rats, however, showed no increase in glucose transport and no increase in the activity of maltase, another brush-border enzyme.
mesh_terms: D000138:Acidosis / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D012964:Sodium / Q000378:metabolism; D005723:gamma-Glutamyltransferase / Q000378:metabolism
chemical_list: D005973:Glutamine; D012964:Sodium; D005723:gamma-Glutamyltransferase