Munck B G, Schultz S G
J Gen Physiol. 1969 Feb;53(2):157-82. doi: 10.1085/jgp.53.2.157.
Lysine transport by in vitro distal rabbit ileum has been investigated by determining (a) transmural fluxes across short-circuited segments of the tissue; (b) accumulation by mucosal strips; and (c) influx from the mucosal solution across the brush border into the epithelium. Net transmural flux of lysine is considerably smaller than that of alanine. However, lysine influx across the brush border and lysine accumulation by mucosal strips are quantitatively comparable to alanine influx and accumulation. Evidence is presented that the "low transport capacity" of rabbit ileum for lysine is due to: (a) a carrier-mediated process responsible for efflux of lysine out of the cell across the serosal and/or lateral membranes that is characterized by a low maximal velocity; and (b) a high "backflux" of lysine out of the cell across the mucosal membrane. A possible explanation for the latter observation is discussed with reference to the relatively low Na dependence of lysine transport across the intestinal brush border.
(a) 跨组织短路段的跨壁通量；(b) 黏膜条带的积累量；以及 (c) 从黏膜溶液穿过刷状缘进入上皮细胞的流入量。赖氨酸的净跨壁通量远小于丙氨酸的净跨壁通量。然而，赖氨酸穿过刷状缘的流入量以及黏膜条带对赖氨酸的积累量在数量上与丙氨酸的流入量和积累量相当。有证据表明，兔回肠对赖氨酸的 “低转运能力” 是由于：(a) 一种载体介导的过程，负责赖氨酸通过浆膜和/或侧膜排出细胞，其特征是最大速度较低；以及 (b) 赖氨酸通过黏膜膜从细胞中的大量 “回流”。参照赖氨酸跨肠刷状缘转运对钠的相对低依赖性，讨论了后一种观察结果的可能解释。
