大鼠空肠对5-甲基四氢叶酸的摄取

Uptake of 5-methyltetrahydrofolic acid by the rat jejunum.

Blair J A, Matty A J, Razzaque A

J Physiol. 1975 Sep;250(2):221-30. doi: 10.1113/jphysiol.1975.sp011050.

Abstract

Everted sacs of rat jejunum were used to study the transport of 5-methyltetrahydrofolic acid at various concentrations and at different pHs. 2. The transport of 5-methyltetrahydrofolic acid appeared to be linear with increasing incubation time at a 5-methyltetrahydrofolic acid concentration of 10(-5) M in the incubating medium. Tissue uptake was much higher than serosal uptake. 3. At 'zero' concentration gradient of 5-methyltetrahydrofolic acid, the transport from mucosal to serosal sides was negligible but tissue uptake was appreciable. 4. Reducing the incubation temperature from 37 to 27 degrees C gave a Q10 value of 1-8. 5. The characteristics of 5-methyltetrahydrofolic acid uptake suggested a non-saturable transport mechanism. 6. Studies were also carried out with isolated mucosal epithelial cells at different incubation times and at different pH values. 7. The over-all results suggest that 5-methyltetrahydrofolic acid transport is most likely a passive diffusion of its zwitterion and also a solvent drag with water flow. 8. The 5-methyltetrahydrofolic acid may be converted to its zwitterion in an acid microclimate at the surface of the intestinal absorbing cell.

摘要

采用大鼠空肠外翻囊来研究不同浓度和不同pH值下5-甲基四氢叶酸的转运情况。2. 在孵育介质中5-甲基四氢叶酸浓度为10(-5) M时，5-甲基四氢叶酸的转运似乎随孵育时间延长呈线性。组织摄取远高于浆膜摄取。3. 在5-甲基四氢叶酸“零”浓度梯度下，从黏膜侧到浆膜侧的转运可忽略不计，但组织摄取明显。4. 将孵育温度从37℃降至27℃，Q10值为1.8。5. 5-甲基四氢叶酸摄取的特征表明其转运机制为非饱和性。6. 还对分离的黏膜上皮细胞在不同孵育时间和不同pH值下进行了研究。7. 总体结果表明，5-甲基四氢叶酸的转运很可能是其两性离子的被动扩散以及随水流的溶剂拖曳作用。8. 5-甲基四氢叶酸可能在肠道吸收细胞表面的酸性微环境中转化为其两性离子。