The influence of cations on the active transport into cells of rat-brain-cortex slices of l-histidine, an amino acid that is not metabolized by this tissue, has been studied. 2. Like other amino acids, l-histidine accumulated in the cells in the presence of glucose in concentrations up to over double that in the incubation medium. 3. The active transport of l-histidine was highest in a medium containing Ca(2+) (3mm). The addition of K(+) (27mm) led to a marked decrease in the intracellular concentration of l-histidine, though the oxygen uptake of the slices was higher. 4. The active l-histidine transport was inhibited by NH(4) (+). The inhibitory effect increased with the NH(4) (+) concentration, being about 25% at 8mm, 65% at 20mm, and 90% at 27 and 50mm. The oxygen uptake of the brain slices was depressed by only 25% by the highest NH(4) (+) concentration used, and less by lower concentrations.
摘要
研究了阳离子对大鼠脑皮质切片中L-组氨酸（一种该组织不能代谢的氨基酸）主动转运进入细胞的影响。2. 与其他氨基酸一样，在有葡萄糖存在的情况下，L-组氨酸在细胞内积累，其浓度高达孵育培养基中浓度的两倍以上。3. L-组氨酸的主动转运在含有3 mM Ca(2+)的培养基中最高。添加27 mM K(+)会导致L-组氨酸细胞内浓度显著降低，尽管切片的耗氧量更高。4. L-组氨酸的主动转运受到NH(4) (+)的抑制。抑制作用随NH(4) (+)浓度增加而增强，在8 mM时约为25%，在20 mM时为65%，在27 mM和50 mM时为90%。所用最高NH(4) (+)浓度仅使脑切片的耗氧量降低25%，较低浓度时降低程度更小。
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