Thomson A B
Q J Exp Physiol. 1984 Jul;69(3):497-505. doi: 10.1113/expphysiol.1984.sp002836.
The kinetic characteristics of the transport of four sugars were determined in rabbit jejunum and ileum. The effective resistance of the intestinal unstirred layer and the rates of uptake of glucose, galactose, 3-O-methyl glucose and fructose were assessed in vitro. The unstirred layer resistance was higher in jejunum than in ileum at all rates of stirring of the bulk phase. The maximal transport rates, Jmd, of galactose and 3-O-methyl glucose were higher than the Jmd of glucose, which in turn was higher than that for fructose. The Jmd of glucose, galactose, and fructose were each lower in ileum than in jejunum, but the Jmd of 3-O-methyl glucose in the ileum was similar to both regions. For the single Michaelis-Menten model, the values of the Michaelis constant, Km, for glucose and galactose were slightly lower in the jejunum than in the ileum, whereas the value of the Km for 3-O-methyl glucose and for fructose were similar in the two sites. In the jejunum, the relative values of the Km were 3-O-methyl glucose = fructose greater than galactose greater than glucose. It is regarded that variations in sugar absorption between the jejunum and ileum are due to differences in the values of the effective resistance of the unstirred water layer, the maximal transport rate, and the Michaelis constant.
测定了四种糖类在兔空肠和回肠中的转运动力学特征。在体外评估了肠道未搅动层的有效阻力以及葡萄糖、半乳糖、3 - O - 甲基葡萄糖和果糖的摄取速率。在本体相的所有搅拌速率下，空肠中未搅动层的阻力均高于回肠。半乳糖和3 - O - 甲基葡萄糖的最大转运速率Jmd高于葡萄糖的Jmd，而葡萄糖的Jmd又高于果糖的Jmd。葡萄糖、半乳糖和果糖的Jmd在回肠中均低于空肠，但回肠中3 - O - 甲基葡萄糖的Jmd在两个区域相似。对于单一的米氏模型，空肠中葡萄糖和半乳糖的米氏常数Km值略低于回肠，而空肠和回肠中3 - O - 甲基葡萄糖和果糖的Km值相似。在空肠中，Km的相对值为3 - O - 甲基葡萄糖 = 果糖＞半乳糖＞葡萄糖。人们认为空肠和回肠之间糖类吸收的差异是由于未搅动水层的有效阻力值、最大转运速率和米氏常数的不同所致。
