Foley M K, Inoue Y, Souba W W, Sarr M G
Department of Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minn. 55905, USA.
Surgery. 1998 Mar;123(3):321-9.
We previously showed a decrease in ileal glutamine transport in vitro and net absorption in vivo after extrinsic denervation of the canine jejunoileum. The aim was to determine whether extrinsic innervation modulates in vivo net absorption and in vitro transport of glutamine and other nutrients in canine jejunum.
In vivo net jejunal uptakes of glutamine, alanine, leucine, and glucose were measured in five dogs before and 2 and 8 weeks after a model neurally isolating in situ the jejunoileum (extrinsic denervation, intestinal transection). 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 with six control dogs with fully intact extrinsic innervation.
In vivo net absorption of glutamine decreased at 2 weeks (p < 0.05) and returned to normal values at 8 weeks; net absorptions of leucine, alanine, and glucose were decreased at both 2 and 8 weeks. In vitro brush border membrane vesicles transport of glutamine, leucine, and alanine followed the patterns of in vivo absorption, but glucose transport did not differ at any time point. Decreased glutamine uptake at 2 weeks resulted from a decrease in Vmax rather than a change in K(m) in sodium-dependent carrier-mediated transport.
Extrinsic denervation 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 transporters.
我们之前发现，犬空肠回肠进行外在去神经支配后，回肠谷氨酰胺的体外转运及体内净吸收均有所下降。本研究旨在确定外在神经支配是否会调节犬空肠谷氨酰胺及其他营养物质的体内净吸收和体外转运。
在五只犬身上，于原位模型神经隔离空肠回肠（外在去神经支配，肠横断）前、术后2周和8周，测量空肠对谷氨酰胺、丙氨酸、亮氨酸和葡萄糖的体内净摄取量。为评估其机制，对六只犬空肠回肠神经隔离前、术后2周和8周的空肠刷状缘膜囊泡中载体介导的摄取进行定量，并与六只具有完整外在神经支配的对照犬进行比较。
谷氨酰胺的体内净吸收在2周时下降（p < 0.05），8周时恢复至正常水平；亮氨酸、丙氨酸和葡萄糖的净吸收在2周和8周时均下降。体外刷状缘膜囊泡对谷氨酰胺、亮氨酸和丙氨酸的转运遵循体内吸收模式，但葡萄糖转运在任何时间点均无差异。2周时谷氨酰胺摄取减少是由于钠依赖性载体介导转运中Vmax降低而非Km改变所致。
外在去神经支配下调了氨基酸的载体介导转运，但未影响葡萄糖的转运。体外谷氨酰胺转运减少部分是由钠依赖性转运体数量减少而非亲和力降低介导的。
