The riciprocity between the Quality of dietary protein and the maintenance of liver enzyme activity in rats have been investigated. The results are as follows: 1) We have found paralleled relation between the xanthine oxidase activity of rat's liver and growth in weanling rats fed the same protein by using 15 kinds of food protein respectively. Arginase, however, hasn't brought us such relation. 2) Next we have found that with the kind of carbohydrate and fat in the diet, there was no influence upon the activity of rat's liver enzyme under fixed condition. Judging from these results, we can presume that under the fixed condition the activity response of rat's liver xanthine oxidase can be used as a criterion for estimation of protein quality.
The suitable level of protein in diet for evaluation of food protein quality by using adult rat's liver enzyme activity as a criterion was examined by using 15 kinds of food proteins. The results are as follows: About xanthine oxidase, the most remarkable paralleled relation between protein quality and enzyme activity were obtained when at 15% and 20% levels of food protein in the diet. About arginase this paralleled relation is found in the case of 20% only. From these results and previously reported results, we have divided 15 kinds of food protein used into groups by using xanthine oxidase activity. The 3 groups are found: the groups of eggs with the highest activity, that of soya beans with middle activity, and that of glutens with the lowest activity. These results tell us that such results almost correspond with the so far well-known nutritive value of food proteins.
Influence of vibration (frequency 12-13/sec., amplitude 1.6-6.8mm, for seven hours daily) on protein metabolism of white rats fed on normal-protein (16%) and low-protein (10%) diets was observed for six weeks. Results shows that under the vibration the nitrogen balance is much more positive in the case of the normal-protein diet than in low-protein diet. In other words, in such a abnormal environment, the animal needs enough protein in order to reach full growth.