Dudeja P K, Wali R K, Klitzke A, Brasitus T A
Department of Medicine, Pritzker School of Medicine, University of Chicago, Illinois 60637.
Am J Physiol. 1990 Oct;259(4 Pt 1):G571-7. doi: 10.1152/ajpgi.1990.259.4.G571.
Diabetes was induced in male Lewis rats by a single injection of streptozocin (50 mg/kg body wt ip). After 10-14 days, diabetic and age- and sex-matched control animals were killed, and their proximal small intestines were removed. Villus-tip, mid-villus, and lower-villus enterocytes were harvested from each group with a method that combined divalent cation chelation with mild mechanical dissociation. These fractions were used as starting material to prepare brush-border membrane vesicles. Preparations from each of these fractions were then analyzed and compared with respect to their Na(+)-gradient-dependent and Na(+)-independent D-glucose transport, lipid fluidity, and lipid composition. The results of these experiments demonstrated that 1) maximum rates of Na(+)-gradient-dependent D-glucose transport (Vmax) were greatest in membrane vesicles prepared from mature cells (villus tip and mid villus) of control rats; 2) the glucose concentration producing half-maximal rates of transport (Km), however, was significantly lower in lower-villus membrane vesicles of control rats, suggesting that a distinct glucose transporter existed in the membranes of these relatively immature enterocytes; 3) Na(+)-gradient-dependent, but not Na(+)-independent, D-glucose uptake was greater in diabetic membrane vesicles prepared from mid-villus and lower-villus fractions but not in vesicles prepared from villus-tip cells; and 4) no obvious relationship between alterations in membrane lipid fluidity and enhanced uptake of Na(+)-gradient-dependent D-glucose by these transporter(s) could be established in this experimental model of acute diabetes mellitus.
通过单次腹腔注射链脲佐菌素（50 mg/kg体重）诱导雄性Lewis大鼠患糖尿病。10 - 14天后，处死糖尿病大鼠以及年龄和性别匹配的对照动物，并取出它们的近端小肠。采用二价阳离子螯合与轻度机械解离相结合的方法，从每组中收集绒毛顶端、绒毛中部和绒毛下部的肠上皮细胞。这些细胞组分用作制备刷状缘膜囊泡的起始材料。然后对这些组分的制备物进行分析，并比较它们的钠梯度依赖性和非钠依赖性D - 葡萄糖转运、脂质流动性和脂质组成。这些实验结果表明：1）对照大鼠成熟细胞（绒毛顶端和绒毛中部）制备的膜囊泡中，钠梯度依赖性D - 葡萄糖转运的最大速率（Vmax）最大；2）然而，对照大鼠绒毛下部膜囊泡中产生半数最大转运速率的葡萄糖浓度（Km）显著更低，这表明这些相对不成熟的肠上皮细胞膜中存在一种独特的葡萄糖转运体；3）从中部绒毛和下部绒毛组分制备的糖尿病膜囊泡中，钠梯度依赖性而非非钠依赖性D - 葡萄糖摄取增加，但从绒毛顶端细胞制备的囊泡中未增加；4）在这个急性糖尿病实验模型中，无法确定膜脂质流动性的改变与这些转运体对钠梯度依赖性D - 葡萄糖摄取增加之间的明显关系。
