Keiichiro Muramatsu

Relationsnip Between the Nutritive Value of Dietary Protein and Liver Xanthine Oxidase Activity in Young Rats

The relationship between the nutritive value of dietary protein and the activity of lievr xanthine oxidase in growing rats as related to the growth rate and the protein efficiency ratio has been investigated.The response curve of liver xanthine oxidase plotted against the protein level in the diet was essentially exponential, and the lower portion of this curve was linear. The slope of this straight portion, i.e., the tangent of the curve was observed to reflect the quality of dietary protein from comparison with the growth rate and the protein efficiency ratio.

Nitrogen Balance and Some Liver Enzymes in Adult Rats

Nitrogen balance is shown by the sum of the retentions and losses involving in all the tissue protein. It is questionable, however, whether or on the values obtained by this method show a true requirement of nitrogen needed for the good health of adult animals.We have studied the relationships between nitrogen balance and the liver nitrogen, and liver xanthine oxidase and succinic dehydrogenase in rats fed on diets containing various levels of casein. We have found that body weight and the liver nitrogen content slightly decreased, and liver xanthine oxidase and succinic dehydrogenase activities decreased considrably at the point of nitrogen equilibrium.

Self-selection of glycine and tyrosine in rats.

非必須アミノ酸 (non-EAA) であるGlyとL-Tyrの選択摂取実験を離乳直後のラットを用いて行いこれまでの必須アミノ酸 (EAA) の結果と比較した。その結果Glyの選択摂取時には7%添加食を忌避したがそれ以下ではGly含量の多い飼料を好んで摂取し, L-Tyrの選択摂取時には3%以上添加した飼料を忌避したがそれ以下ではL-Tyr含量の多い飼料を好んで摂取した。このような結果から, ラットはGly, L-Tyrのようなnon-EAAについても過剰摂取による害作用を防止する機構により最大摂取量を調節する能力を有していることが明らかになった。

Composition of Nutrients and Metabolism of Tissue Protein

Relation between the amounts of dietary protein and enzyme activity was examined by using arbino rats. Casein fed as the source of proiein at levels of 0, 15, 30, 40, 60 and 80 per cent in the diet for eighteen days. Liver xanthine oxidase which is considered to be relate with the metabolism of nuclepprotein was chosen for the enzyme of this experiment. The enzyme activity was measured by a modification of manometric method of AXELROD-ELVEHJEM and colorimetric `method of LITWACK et al. A corelation has been found between these methods. The results showed that the enzyme respons was very sensitive to changes in the content of protein in diets and depleted to “zero” levels at the protein free ration (Table 2). From the values of enzyme activity which was plotted aganist the level of dietary protein (casein) fed, we found that xanthine oxidase activity was increased according to the amount of protein, but no change took place in greater amount than about 30 per cent protein in diet (Fig. 2). The authors suggested that feeding of dietary protein which maintained the stationary level of xanthine oxidase activity was required.