Transcellular mechanisms of amino acid uptake by distal rat ileum in situ.
A 10 cm distal ileal intestinal perfusion technique was employed in Sprague-Dawley rats in situ. The perfused segment was removed, weighed, its surface area measured, homogenized, digested in HNO3 and assayed for L(1-14C)alanine and L-phenyl (1-14C)alanine. Steady state for L-alanine and L-phenylalanine absorption by the intact intestinal segment was observed at 10 and 15 min respectively. Exposure of the intestinal mucosa to 1 mM ouabain showed no effect on amino acid absorption. Preloading the intestinal epithelium with ouabain resulted in approximately 66% and 48% reduction in L-alanine and L-phenylalanine absorption respectively. Removal of Na from the buffer with and without exposure of the mucosa to 1 mM ouabain decreased absorption of L-alanine and L-phenylalanine by approximately 77% and 52% respectively. Removal of Na from the buffer and preloading the intestinal epithelium with ouabain resulted in approximately 85% and 81% reduction in L-alanine and L-phenylalanine absorption respectively. A 5, 10 and 25 fold increase in luminal L-alanine and L-phenylalanine concentration in Na-free choline Krebs Ringer after preloading with ouabain resulted in increase of amino acid absorption of approximately the same order of magnitude. Both an amino acid-carrier mediated transport process and a ouabain resistant Na-dependent-amino acid pump exist at the mucosal side. Both an ouabain sensitive Na-dependent-amino acid pump and an ouabain resistant Na-independent amino acid pump exist at the serosal side. Approximately 15-20% of absorbed amino acids are passively translocated.
Bikhazi
A B
AB
Abu Salbi
M N
MN
Itani
J H
JH
D000409:Alanine / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D007082:Ileum / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D010477:Perfusion; D010649:Phenylalanine / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology
D000596:Amino Acids; D010649:Phenylalanine; D010042:Ouabain; D012964:Sodium; D000409:Alanine