A significant proportion of plasma zinc exists complexed with amino acids. The effect of amino acids on the accumulation of radioactive zinc by rat erythrocytes was studied in vitro, to investigate the hypothesis that zinc might be transported into cells as an amino acid-zinc complex. 2. L-Histidine (500 microM-10 mM) stimulated 65Zn uptake; 50 mM-L-histidine gave a slight inhibition of uptake. D-Histidine (500 microM-10 mM) inhibited uptake in a dose-dependent manner. A non-zinc-binding amino acid, L-alanine, did not affect 65Zn uptake. 3. The effect of L-histidine was sodium dependent and temperature dependent, but was DIDS insensitive. These properties suggest that zinc is being transported as a zinc-histidine complex, utilizing an amino acid carrier system. Uptake of zinc in the presence of L-histidine differed from the previously described ionic mechanism, and may represent a physiological route of uptake. 4. L-Histidine stimulated efflux of 65Zn from pre-loaded cells. 5. The relevance of transport of a zinc-histidine complex is discussed with reference to histidinaemia, and as a significant zinc transport system in the presence of the very low ionic zinc concentrations found in plasma.
摘要
相当一部分血浆锌以与氨基酸络合的形式存在。在体外研究了氨基酸对大鼠红细胞摄取放射性锌的影响，以探究锌可能作为氨基酸 - 锌络合物转运进入细胞的假说。2. L - 组氨酸（500微摩尔/升 - 10毫摩尔/升）刺激了65锌的摄取；50毫摩尔/升的L - 组氨酸对摄取有轻微抑制作用。D - 组氨酸（500微摩尔/升 - 10毫摩尔/升）以剂量依赖方式抑制摄取。一种非锌结合氨基酸L - 丙氨酸对65锌的摄取没有影响。3. L - 组氨酸的作用依赖于钠和温度，但对二异丙基氟磷酸（DIDS）不敏感。这些特性表明锌作为锌 - 组氨酸络合物被转运，利用了一种氨基酸载体系统。在L - 组氨酸存在下锌的摄取不同于先前描述的离子机制，可能代表一种生理摄取途径。4. L - 组氨酸刺激了预先加载细胞中65锌的外流。5. 参照组氨酸血症讨论了锌 - 组氨酸络合物转运的相关性，并将其作为在血浆中发现的极低离子锌浓度情况下的一种重要锌转运系统。
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