Fleet J C, Andrews G K, McCormick C C
Department of Poultry and Avian Sciences, Cornell University, Ithaca, NY 14853.
J Nutr. 1990 Oct;120(10):1214-22. doi: 10.1093/jn/120.10.1214.
The induction of hepatic metallothionein (MT) by the parenteral administration of iron was studied. Iron administered to chicks by intravenous or subcutaneous injection caused a 1.9-fold increase in hepatic MT. In marked contrast, intraperitoneal (ip) Fe resulted in a 10-fold increase, thus demonstrating the importance of the route of metal administration. This route-dependent effect was found to be dose-dependent, with ip injections between 1 and 10 mg Fe/kg resulting in a linear increase in MT and a concomitant reduction in serum zinc concentration and feed intake. High ip doses of Fe resulted in a persistent depression in serum Zn and elevated MT and MTmRNA. Equimolar ip injections of either Zn or Fe showed similar patterns of MTmRNA accumulation. In both cases MTmRNA levels were elevated by 3 h, with a peak at 6 h postinjection (Fe 8-fold, Zn 12-fold above 0 h). Plasma Zn was maximally reduced by Fe at 9 h (60%). The MT induction by Fe, as well as related depression in plasma Zn, was completely inhibited by actinomycin D. Zn depletion eliminated the accumulation of hepatic Zn and MT protein following ip injection of Fe or endotoxin, but not of cadmium, despite marked elevation of hepatic MTmRNA. Our results demonstrate Fe injected into the body cavity of chicks results in a rapid induction of hepatic MT that, like endotoxin induction, is independent of dietary Zn status.
研究了通过胃肠外给予铁来诱导肝脏金属硫蛋白（MT）的情况。通过静脉注射或皮下注射给雏鸡补铁，可使肝脏MT增加1.9倍。与之形成显著对比的是，腹腔注射铁可使MT增加10倍，从而证明了金属给药途径的重要性。发现这种途径依赖性效应是剂量依赖性的，腹腔注射1至10毫克铁/千克会使MT呈线性增加，并伴随血清锌浓度和采食量降低。腹腔注射高剂量铁会导致血清锌持续降低，MT和MTmRNA升高。等摩尔腹腔注射锌或铁显示出相似的MTmRNA积累模式。在这两种情况下，MTmRNA水平在注射后3小时升高，在注射后6小时达到峰值（铁比0小时高8倍，锌比0小时高12倍）。铁在9小时时使血浆锌最大程度降低（60%）。铁诱导MT以及血浆锌相关降低的现象被放线菌素D完全抑制。锌缺乏消除了腹腔注射铁或内毒素后肝脏锌和MT蛋白的积累，但腹腔注射镉后没有消除，尽管肝脏MTmRNA显著升高。我们的结果表明，向雏鸡体腔注射铁会导致肝脏MT快速诱导，这与内毒素诱导一样，与日粮锌状态无关。
