EXTRINSIC INNERVATION MODULATES CANINE JEJUNAL TRANSPORT OF GLUTAMINE, ALANINE, LEUCINE, AND GLUCOSE

Background, We previously showed a decrease in ileal glutamine transpo rt in vitro and net absorption in vivo after extrinsic denervation of the canine jejunoileum. The aim was to determine whether extrinsic inn ervation modulates in vivo net absorption and in vitro transport of gl utamine end other nutrients in canine jejunum. Methods. In vivo net je junal uptakes of glutamine, alanine, leucine, and glucose were measure d in five dogs before and 2 and 8 weeks after a model neurally isolati ng-in situ the jejunoileum (extrinsic denervation, intestinal transect ion). To assess mechanisms, carrier-mediated uptakes were quantitated in jejunal brush border membrane vesicles from six dogs before and at 2 and 8 weeks after neural isolation of the jejunoileum and compared w ith six control dogs with fully intact extrinsic innervation Results. In vivo net absorption of glutamine decreased at 2 weeks (p < 0.05) an d returned to normal values at 8 weeks; net absorptions of leucine, al anine, and glucose were decreased at both 2 and 8 weeks. In vitro brus h border membrane vesicles transport of glutamine, leucine, and alanin e followed the patterns of in vivo absorption, but glucose transport d id not differ at any time point. Decreased glutamine uptake at 2 weeks resulted from a decrease in V-max rather than a change in K-m in sodi um-dependent carrier-mediated transport. Conclusions, Extrinsic denerv ation down-regulated carrier-mediated transport of amino acids but not glucose. Decreased in vitro glutamine transport was mediated in part by a decrease in number rather than affinity of sodium-dependent trans porters.