Amino acid flux in ruminal and gastric veins of sheep: effects of ruminal and omasal injections of free amino acids and carnosine.
The possibility of free amino acid (FAA) and peptide absorption across the ruminant stomach wall was studied in multicatheterized wethers fed every 12 h. During the last third of the feeding cycle, two intraruminal or intraomasal injections of solutions containing increasing amounts of Ser, Gly, Val, Met, Phe, Lys, and carnosine were successively performed. Before injections, a net uptake of each of these FAA was measured in the ruminal and the gastric veins. The ruminal injections produced a linear increase in ruminal FAA concentration. The highest ruminal concentrations (observed with 3 g of FAA and carnosine) ranged between 5 and 14 mM. After ruminal injections, Ser (P < .05), Gly (P < .05), Val (P < .05), Met (P < .10), and Lys (P < .10) uptake decreased and carnosine net release linearly increased (P < .05), suggesting absorption across the ruminal epithelium. Owing to the low net flux generated by high ruminal concentration, the ruminal epithelium permeability to these molecules seemed to be low. After omasal injections, net flux of injected FAA were not modified, suggesting a low permeability of the gastric epithelia to FAA. Carnosine net release linearily increased (P < .05) with increasing level of carnosine injection, indicating the possibility of dipeptide absorption at the gastric level. This study demonstrated in vivo that the stomach epithelia possess the capacity to absorb FAA and small peptides; however, the permeability of these epithelia to these molecules seemed limited.
Rémond
D
D
Unité de Recherches sur les Herbivores, Institut National de la Recherche Agronomique de Clermont-Ferrand, Genès-Champanelle, France. dremond@clermont.inra.fr
Bernard
L
L
Poncet
C
C
D000042:Absorption; D000596:Amino Acids / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D002336:Carnosine / Q000008:administration & dosage / Q000494:pharmacology*; D007267:Injections; D008297:Male; D009851:Omasum; D010455:Peptides / Q000378:metabolism; D012039:Regional Blood Flow; D012417:Rumen / Q000378:metabolism*; D012756:Sheep / Q000097:blood / Q000378:metabolism*; D013270:Stomach / Q000098:blood supply*; D014680:Veins
D000596:Amino Acids; D010455:Peptides; D002336:Carnosine