| Metallothionein (MT) is a low-molecular-weight (about 6500Da), composed of about sixty-one amino acid. One MT can bind seven metals. Under natural conditions, MT is a zinc-or copper- and zinc-binding protein. It has an important function in the transport and saving of zinc. In order to study the effect of zinc status on MT, mice were used as animal model, and three experiments were conducted.1 Combined with serum alkaline phosphatase to study on the days of zinc exhaustion. In this study, ten Kun Ming male mice weighing 13~14g, with 21 d on arrival, were housed in plastic metabolic cages respectively. Mice were given purified diet (based on casein and corn starch containing 2.13mg Zn/kg) . Following the 0- 5^ 10, 15d feeding period, two mice were killed by respectively, the serum was made. Combined with serum alkaline phosphatase to determine the days in with serum alkaline phosphatase was at the end of normal physiological limits. The result of this experiment show: the level of serum alkaline phosphatase was at the end of normal physiological limits after ten days of zinc deficiency, the level of serum alkaline phosphatase would increase with days of zinc deficiency.2 At the base of zinc exhaustion, thirty Kun Ming male mice weighing 13~14g, with 21-d on arrival, were housed in plastic metabolic cages respectively. Those mice were divided randomly into groups. The mice of the first group were fed a purified diet containing 30mg Zn/kg. The second group was pair-fed group the mice of which were fed with 30mg Zn/kg diet, which supplied adequate levels of zinc, but the food intake was limited to equal to the last group, in order to eliminate differences in diet intake. The last group of mice was fed with 2.13mg Zn/kg diet to induce zinc deficiency. The results of this experiment show:1) The ratio of Zn and Cu binding to MT was different among tissues. Under natural conditions, the ratio of plasma was one to three, the ratio of liver and small intestine was three to one, and the ratio of kidney was about one to one. Stress of food intake limit and zinc deficiency can increase the proportion of Zn-binding in plasma, liver, kidney and small intestine MT. In the pair-fed group the ratio of liver was about six to one, kidney was two to one, plasma and small intestine were all Zn-MT. In the zinc deficiency plasma liver kidney and small intestine were all Zn-MT.2) Ten days of food intake limit cause plasma MT content increased, viscera MT content decreased, but at 20th day, plasma MT content was decreasing to under the control group,but the liver, kidney and small intestine MT content increased respectively 63.63% 20.85%10.59%.3) During the whole experiment, zinc deficient group's viscera MT content always lower than that of control group. But with the increasing of experiment period, small intestine MT content decreased 30.82%, plasma MT content increased 63.63%, liver MT content increased 20.85%, kidney MT content increased 10.59%.4) Small intestine MT content at 10th day can indicates zinc deficiency, but can not be used to distinguish the stress of food intake limit and zinc deficiency. But after twenty days, plasma MT content can be used to assess zinc deficiency, plasma MT content increased more significantly during zinc deficiency, but it would decrease during stress of food intake limit; MT content of liver and small intestine changed insignificantly in different treatments, but they can be used to estimate zinc deficiency, zinc deficiency can make MT content of liver and small intestine decrease slightly, but the stress of food intake limit can make a different result.5) Except kidney, plasma, liver and small intestine Zn-MT can't be used to assess zinc deficiency alone. But Zn-MT content can be used to increase the precision of MT assessment.3 At the base of zinc exhaustion, by feeding with purified diet containing 10 30 50 70 90 J10 N 150mg Zn/kg to study the interrelation between MT Zn-MT and diet zinc content. The results show:The interrelation between MT and diet... |
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