Zinc is one of the essential trace elements in the living organism for gro"vth and health. The first identified meta lleenzvme, carbonic anhvdrase, is a zinc compound and several others have been described since. Among zinc deficiency syndromes in animals porcine parakeratesis has been successfully treated with zinc supplements, and in man a syndrome of anemia, hypogonadism, hepatesplenomegaly, and dwarfism, prevalent in parts of Iran and Egypt, has been ascribed to lack of zinc in the diet.
Dietary zinc excess in the rat is manifested by a hypochromic, micrccvtic anemia, poor growth, reduction in liver catalase and cytochrome oxidase.
The present study is an attempt to delineate the changes of tissue contents of trace elements. especially of iron, copper and zinc in liver and kidneys of the rats.
Weanling albino rats, weighing 60 to 80gm. were used in this experiments. The rats were housed to cages with aluminum floors and received feed and distilled water ad libitum. Animals were divided into three groups, control, low zinc diet and high zinc diet groups. The high zinc diet group was subdivided into 0.5% Zn and 0. 7oZn groups. The supplementary copper or iron was added to the high dietary zinc groups.
The animals were sacrificed and the tissues were washed several times with deionized ,,eater. The wet digested samples were analyzed by Hitachi Model 207 atomic absorption spectre-phctometer for the determination of iron, copper and zinc in the liver and kidney. Hemoglobin level in the blood was measured by cyanmethemoglobin method.
The results of this study are as follows:
1) All rats fed high zinc diets and low zinc diets gained less weight than control. Weight gain was not improved by the supplementary copper or iron and both.
2) Hemoglobin concentration was decreased significantly in the rats fed high zinc diets and less in the low zinc diets. Supplementary copper and iron to the higher zinc diet appeared to give sorne improvement of anemia.
3) The iron contents of the liver and kidneys were significantly decreased in the high zinc groups and
the reduction was more significantly in the rats receiving higher zinc diet (0.7%). The supplementary copper caused a further depression of liver iron. On the other hand, the iron, added to the high zinc diet lessened the severity of the decrease in liver iron and caused kidney iron to be maintained almost at the level found in the rats fed by zinc and supplementary copper diet.
4) High zinc diets did not change copper content of the liver and kidney. Supplementary copper elevated the concentration in the liver and kidney and added iron had no effect on the accumulation of copper in the liver and kidneys.
5) The high zinc diets caused marked increases of zinc content in the liver and kidney. Supplementary iron to the high zinc diet caused increases of zinc contents of liver and kidneys.
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