Munck B G, Rasmussen S N
J Physiol. 1979 Jun;291:291-303. doi: 10.1113/jphysiol.1979.sp012813.
Transport of lysine across the rat jejunum has been studied measuring transmural fluxes, Jms and Jsm, under short-circuit conditions, influx across the brush-border membrane, Jmc, under open-circuit and voltage-clamp conditions, and steady-state uptake by the isolated mucosa. 1. Jlysmc can be described as the sum of a saturable process with a Kt of 3 mM and a Jmax of 2.25 micromole/cm2.hr and a diffusional component corresponding to a lysine permeability of 0.014 cm/hr. Also Jlysms is well described as the sum of a saturable process and a diffusional contribution described by the same permeability as for Jlysmc. 2. The effects of the transmural p.d. on Jlysmc indicate that at 60 mM this flux includes a diffusional contribution, which corresponds to a lysine permeability of 0.014 cm/hr. 3. The passage of an electrical current across the gut wall changes the electrical conductance as expected for a cation-selective epithelium. The effect of a mucosa to serosa current on the Jms value of mannitol provides confirmation of the expected current effect on transepithelial volume flow. These effects on conductance and solute flux, together with the electrostatic effect on lysine movements, suffice to account for the p.d. effects on Jmc, Jms, and Jsm of lysine. 4. Jlyssm is in a saturable manner stimulated by increasing concentrations of D-glucose. At higher (10 mM) concentrations of lysine this effect leads to a net secretion of lysine. Qualitatively and quantitatively these effects are consistent with the model of a glucose-induced fluid circuit between the mucosal solution and the lateral intercellular spaces. 5. All observations are consistent with a paracellular, transepithelial pathway for lysine, which includes the lateral intercellular spaces. 6. The transport of lysine across the basolateral membrane is analysed. Togethet the data on transcellular passage of lysine are very similar to those reported for rabbit ileum, except that more than one transport process could not be demonstrated.
通过测量短路条件下的跨壁通量Jms和Jsm、开路和电压钳制条件下穿过刷状缘膜的流入量Jmc以及分离黏膜的稳态摄取量，对赖氨酸在大鼠空肠中的转运进行了研究。1. Jlysmc可描述为一个Kt为3 mM、Jmax为2.25微摩尔/平方厘米·小时的可饱和过程与一个对应赖氨酸渗透率为0.014厘米/小时的扩散成分之和。同样，Jlysms也很好地描述为一个可饱和过程与一个由与Jlysmc相同渗透率描述的扩散贡献之和。2. 跨壁电位对Jlysmc的影响表明，在60 mM时，该通量包括一个扩散贡献，对应赖氨酸渗透率为0.014厘米/小时。3. 电流通过肠壁会改变电导，这符合阳离子选择性上皮的预期。黏膜到浆膜电流对甘露醇Jms值的影响证实了预期的电流对跨上皮体积流的影响。这些对电导和溶质通量的影响，以及对赖氨酸运动的静电效应，足以解释电位对赖氨酸Jmc、Jms和Jsm的影响。4. Jlyssm以可饱和的方式受到D - 葡萄糖浓度增加的刺激。在较高（10 mM）的赖氨酸浓度下，这种效应导致赖氨酸的净分泌。这些效应在定性和定量上与黏膜溶液和细胞间侧隙之间葡萄糖诱导的流体回路模型一致。5. 所有观察结果都与赖氨酸通过包括细胞间侧隙的细胞旁跨上皮途径一致。6. 分析了赖氨酸跨基底外侧膜的转运。总的来说，赖氨酸跨细胞转运的数据与报道的兔回肠的数据非常相似，只是无法证明存在不止一种转运过程。
