Hoadley J E, Leinart A S, Cousins R J
Food Science and Human Nutrition Department, University of Florida, Gainesville 32611.
J Nutr. 1988 Apr;118(4):497-502. doi: 10.1093/jn/118.4.497.
Intestinal 65Zn transport and metallothionein levels were examined in rats fed zinc-adequate and zinc-deficient diets and in rats subjected to an overnight fast. 65Zn uptake by intestines perfused with 1.5 microM 65Zn was greater in both zinc-deficient and fasted groups than in the control group. Mucosal retention of 65Zn was also greater in the zinc-deficient group but not in the fasted group. The greater 65Zn uptake in the fasted group was associated with a compartment that readily released 65Zn back into the lumen. Kinetic analysis of the rate of 65Zn transfer to the vascular space (absorption) showed that 65Zn absorption involved approximately 3% of mucosal 65Zn in a 40-min perfusion period. The half-life (t1/2) of this mucosal 65Zn rapid transport pool corresponded directly to changes in intestinal metallothionein levels. Both metallothionein and t1/2 were higher in the fasted group and lower in the zinc-deficient group than in controls. While the rate of 65Zn transport from this rapid transport pool decreased with increasing metallothionein level, the predicted pool size increased when the metallothionein level was elevated by fasting. These results indicate that the rate of zinc absorption is inversely related to intestinal metallothionein levels, but the portion of mucosal 65Zn available for absorption is directly related to intestinal metallothionein.
对喂食锌充足和锌缺乏饮食的大鼠以及禁食过夜的大鼠的肠道65锌转运和金属硫蛋白水平进行了检测。用1.5微摩尔65锌灌注的肠道对65锌的摄取在锌缺乏组和禁食组中均高于对照组。锌缺乏组中65锌的黏膜保留量也更高，但禁食组中则不然。禁食组中65锌摄取量增加与一个易于将65锌释放回肠腔的区室有关。对65锌向血管空间转移（吸收）速率的动力学分析表明，在40分钟的灌注期内，65锌吸收涉及约3%的黏膜65锌。这个黏膜65锌快速转运池的半衰期（t1/2）与肠道金属硫蛋白水平的变化直接相关。禁食组中的金属硫蛋白和t1/2均高于对照组，而锌缺乏组则低于对照组。虽然从这个快速转运池转运65锌的速率随着金属硫蛋白水平的升高而降低，但禁食使金属硫蛋白水平升高时，预测的转运池大小增加。这些结果表明，锌吸收速率与肠道金属硫蛋白水平呈负相关，但可用于吸收的黏膜65锌部分与肠道金属硫蛋白直接相关。
