Smithson K W, Millar D B, Jacobs L R, Gray G M
Science. 1981 Dec 11;214(4526):1241-4. doi: 10.1126/science.7302593.
The dimensions of the small intestinal diffusion barrier interposed between luminal nutrients and their membrane receptors were determined from kinetic analysis of substrate hydrolysis by integral surface membrane enzymes. The calculated equivalent thickness of the unstirred water layer was too large to be compatible with the known dimensions of rat intestine. The discrepancy could be reconciled by consideration of the mucous coat overlying the intestinal surface membrane. Integral surface membrane proteins could not be labeled by an iodine-125 probe unless the surface coat was first removed. The mucoprotein surface coat appears to constitute an important diffusion barrier for nutrients seeking their digestive and transport sites on the outer intestinal membrane.
通过对完整表面膜酶催化底物水解的动力学分析，确定了介于肠腔营养物质与其膜受体之间的小肠扩散屏障的尺寸。计算得出的未搅拌水层等效厚度过大，与大鼠肠道的已知尺寸不相符。考虑覆盖在肠道表面膜上的黏液层，这种差异可以得到解释。除非首先去除表面涂层，否则完整的表面膜蛋白不能被碘 - 125探针标记。黏蛋白表面涂层似乎构成了营养物质在肠外膜上寻找其消化和转运位点的重要扩散屏障。
