Na+-dependent and Na+-independent transport of L-arginine and L-alanine across dog intestinal brush border membrane vesicles

We prepared intestinal brush border membrane Vesicles (BBMVs) from beagle d ogs fed a commercial diet (protein content: 24-26%), and investigated the c haracteristics of transport for basic and neutral amino acids across the in testinal BBMVs. To determined the kinetic parameters for L-arginine and L-a lanine uptake, their total uptake was resolved into three routes: (1) Na+-d ependent carrier-mediated transport; (2) Na+-independent carrier-mediated t ransport; and (3) simple diffusion. We could observe subtle, but clear-cut, Na+-dependent basic amino acid transport for the first time among studies with intestinal BBMVs prepared from mammals fed a normal diet. The Na+-depe ndent system for L-arginine transport can be best characterized as 'low aff inity, low capacity', in contrast to that for L-alanine transport, which is 'low affinity, high capacity'. Maximal velocities of the Na+-dependent car rier-mediated transport are estimated to be higher for both L-arginine and L-alanine in dog intestinal BBMVs than in rabbit intestinal BBMVs reported previously. These results suggest that food habit of mammals is an importan t factor to decide the characteristic of system B-0,B-+, a Na+-dependent ca rrier-mediated transport system common to basic and neutral amino acids acr oss intestinal brush border membranes, as is protein content of the diet. ( C) 1999 Elsevier Science Inc. All rights reserved.