Murray A J, Nield M K, Jones L M, Galbraith N, Tomas F M
Biochem J. 1985 Dec 1;232(2):409-13. doi: 10.1042/bj2320409.
Mice and rats were injected with tracer doses of radioactive N tau-[Me-14C]methylhistidine in order to determine the recovery of the injected radioactivity and the extent of the metabolism of N tau-methylhistidine. In the first 27 h after injection, 96.3, 78.0 and 97.5% of radioactivity was excreted by female mice, male mice and male rats respectively. Recovery after 5 days of collection was 98.4 and 92.8% for female and male mice respectively. However, radioactivity associated with N tau-methylhistidine or its acetylated derivative accounted for 44, 86.5 and 96.0% of the excreted radioactivity for female mice, male mice and rats respectively. In female mice the remaining excreted radioactivity was associated with four major peaks of activity when the metabolites were separated by cation-exchange chromatography. In male mice there were only three of these metabolites present. After chromatographic purification, one metabolite was identified by mass spectroscopy to be 1-methylimidazole-4-acetic acid. Examination of the possible sources of this metabolite indicates that, in mice, N tau-methylhistidine is decarboxylated and enters the chain of reactions common to histamine metabolism. Such extensive metabolism precludes the use of N tau-methylhistidine excretion as an index of myofibrillar protein breakdown in mice.
给小鼠和大鼠注射微量放射性Nτ-[甲基-¹⁴C]甲基组氨酸，以确定注射放射性的回收率以及Nτ-甲基组氨酸的代谢程度。注射后的前27小时，雌性小鼠、雄性小鼠和雄性大鼠分别排泄了96.3%、78.0%和97.5%的放射性。收集5天后，雌性和雄性小鼠的回收率分别为98.4%和92.8%。然而，与Nτ-甲基组氨酸或其乙酰化衍生物相关的放射性分别占雌性小鼠、雄性小鼠和大鼠排泄放射性的44%、86.5%和96.0%。当通过阳离子交换色谱法分离代谢产物时，雌性小鼠中其余排泄的放射性与四个主要活性峰相关。雄性小鼠中仅存在其中三种代谢产物。经色谱纯化后，通过质谱鉴定出一种代谢产物为1-甲基咪唑-4-乙酸。对该代谢产物可能来源的研究表明，在小鼠中，Nτ-甲基组氨酸脱羧并进入组胺代谢的常见反应链。这种广泛的代谢使得不能将Nτ-甲基组氨酸排泄用作小鼠肌原纤维蛋白分解的指标。
