Miyata S, Inada M
J Nutr Sci Vitaminol (Tokyo). 1976;22(3):187-200. doi: 10.3177/jnsv.22.187.
A brush border preparation from rat intestine was incubated with rat intrinsic factor-vitamin B12 complex in 0.01 M Tris-HCl buffer, pH 7.4. The 57Co-B12 uptake to brush borders was proportional to the amount of protein or to alkaline phosphatase activity in the preparations. The uptake increased with time of incubation. At 37degreesC, the uptake after incubation for 15 min was 80-85% of that for one hr. The uptake at 4degreesC was approximately 70% of that at 37degreesC. Ther was no difference as a result of adding glucose to the incubation medium. The uptake was observed in the alkaline environment above pH 6.3. Maximum uptake occurred at pH 8.0. Brush borders washed with Krebs-Ringer bicarbonate buffer (pH 7.4) exhibited no difference in B12 uptake, whether in the presence or absence of calcium ion. But brush borders washed with ethylenediaminetetraacetate exhibited no uptake when incubated in calcium-free medium. The uptake reached a maximum by addition of calcium ion at a concentration of 0.3 mM, and was not alter up to 10 mM. Addition of magnesium ion exhibited no uptake. Calcium-dependent B12 uptake was markedly inhibited by manganese ion. Magnesium ion seemed to slightly inhibit the calcium-dependent uptake.
将大鼠肠道的刷状缘制剂与大鼠内因子 - 维生素B12复合物在pH 7.4的0.01 M Tris - HCl缓冲液中孵育。57Co - B12对刷状缘的摄取与制剂中的蛋白量或碱性磷酸酶活性成正比。摄取量随孵育时间增加。在37℃时，孵育15分钟后的摄取量是孵育1小时摄取量的80 - 85%。在4℃时的摄取量约为37℃时的70%。向孵育培养基中添加葡萄糖后摄取量无差异。在pH 6.3以上的碱性环境中可观察到摄取。在pH 8.0时摄取量最大。用Krebs - Ringer碳酸氢盐缓冲液（pH 7.4）洗涤的刷状缘，无论有无钙离子存在，其B12摄取均无差异。但用乙二胺四乙酸洗涤的刷状缘在无钙培养基中孵育时无摄取。添加浓度为0.3 mM的钙离子时摄取量达到最大，在10 mM时摄取量不变。添加镁离子时无摄取。锰离子显著抑制钙离子依赖性的B12摄取。镁离子似乎轻微抑制钙离子依赖性摄取。
