ラットの銅代謝に影響する諸要因に関する研究

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Urinary copper excretion has not drawn much attention since its amount has been considered "negligible." Most of copper ingested is excreted in the feces. However, the present author was interested in finding in urinary copper the source of information concerning copper status of the animal. Two types of urine-feces separators for the rats, the funnel-type and the sheet glass-type, were contrived for use in trace element balance studies. The sheet glass-type more satisfactorily separated urine and feces. Using these apparatuses, experiments on copper metabolism were conducted with rats. The following are the results. 1) The rats excreted 80 to 100% of the dietary copper in the feces over the wide range of copper intake. 2) Daily amount of urinary copper remained nearly constant when the rats were copper-adequate. 5) Apparent availability of copper was not affected by the chemical forms of copper. 4) Serum copper level and urinary copper level decreased in parallel when the dietary copper level was lowered to between 0.6 and 1.6 ppm in the adult male rats, between 0.6 and 1.1 ppm in the adult female rats, and between 0.9 and 1.2 ppm in the young male rats. 5) When young male rats were fed with copper-deficient diet, their serum copper, serum ceruloplasmin and urinary copper levels began to decrease rapidly within three days, while their liver copper levels 'decreased very slowly. Adult female rats, when fed with copper-deficient diet, decreased their serum copper and ceruloplasmin levels very slowly. 6) When copper-deficient young male rats were dosed orally with an abundant amount of copper, their serum copper level recovered to 80 % of the normal level, and their serum ceruloplasmin level recovered to 60 % of the normal level within 24 hours. 7) The rats which were given 40 ml/day of water added to the diet excreted two to three times as much urine as those given 20 ml/day of water. However, no difference was found in the daily amount of urinary copper between these two groups, either copper-adequate or copper-deficient. 8) Male rats excreted more copper in urine than females. Even when urinary copper level was factored by body weight or metabolic body size, the value for the males was still higher. 9) Dietary zinc of 8000 ppm severely decreased serum copper and ceruloplasmin, but it gave no influence on urinary copper. Dietary zinc of 4000 ppm or less did not have much effect on copper metabolism of the rats. 10) Dietary molybdenum of 800 ppm decreased serum ceruloplasmin-to-copper ratio, but it had little effect on serum whole copper concentration and body weight gain. These results assured that copper deficiency could be diagnosed by the decrease of urinary copper excretion. It can be said that when a rat excretes half as much urinary copper as the normal rat, it is copper-deficient. This means of diagnosis is especially recommendable for small animals, which would easily suffer from repeated bleeding. In case of complicated copper deficiency, as observed in this study with zinc-intoxicated rats, urinary copper does not decrease while serum whole copper and serum ceruloplasmin decrease severely. It suggests disturbance in the equilibrium between the direct-reacting fraction and ceruloplasmin fraction of serum copper. There exists a critical value of dietary copper level above which serum copper level is maintained constant, and below which serum copper decreases to a very low level. This critical value for young male rats was assumed to exist between 0.9 and 1.2 ppm.
石川県農業短期大学の論文
1977-06-20

著者

加藤啓介
石川県農業短期大学畜産物利用学研究室

ラットの銅代謝に影響する諸要因に関する研究

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