Diminished brush border membrane Na-dependent L-alanine transport in acute viral enteritis in piglets.
We studied sodium-dependent uptake of L-alanine into small intestinal brush border membrane vesicles (BBMV) isolated from piglets 40 h after infection with transmissible gastroenteritis (TGE) virus. Vesicles from TGE-infected pigs and uninfected litter-mate controls showed comparable degrees of enrichment and purity. In BBMV prepared by conventional techniques, [3H]L-alanine "overshoot" (peak uptake/equilibrium uptake) in the presence of a Na gradient was preserved in TGE BBMV, unlike [3H]D-glucose "overshoot," which was reduced. When these experiments were repeated using vesicles of greater purity, initial rates of Na-dependent L-alanine influx were reduced in BBMV from infected piglets under voltage clamped conditions with valinomycin. These studies demonstrate a specific amino acid transport defect in the small intestinal epithelium during acute viral diarrhea. They demonstrate too that brush border L-alanine-Na co-transport, although reduced, is present after viral damage, confirming previous studies that showed additive effects of amino acid and glucose on jejunal epithelial Na+ transport in transmissible gastroenteritis. Our findings support the concept that, in viral enteritis, oral rehydration solutions containing amino acid and glucose have a theoretical advantage over glucose electrolyte solutions because they facilitate brush border Na+ entry by two carrier mechanisms.
Rhoads
J M
JM
Department of Pediatrics, Hospital for Sick Children, University of Toronto, Ontario, Canada.
MacLeod
R J
RJ
Hamilton
J R
JR
D000208:Acute Disease; D000409:Alanine / Q000493:pharmacokinetics*; D000818:Animals; D001692:Biological Transport; D005761:Gastroenteritis, Transmissible, of Swine / Q000378:metabolism*; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013552:Swine
D012964:Sodium; D000409:Alanine