Microbiological assay of the essential amino acids was carried out on a 10% protein diet containing 80% rice and 6% soybean meal. The most limitng essential amino acid according to the value recommended by Rose was found to be methionine(0.09%), the second was lysine(0.29%), and the third histidine(0.23%).The animal experiment consisted of 2 parts. In the first the effect of adding 0.3, 0.6, 0.9 and 1.8g% of DL-methionine to the basal diet was observed upon the growth of weanling albino rats for a two-week period.Results revealed that supplementation of methionine at all level tended to dep- ress growth of rats, especially at the 1.8% level, i.e. an average of 7g gain per two weeks compared with 29g of control group when no methionine was added.In the second part the effect of supplementing lysine or histidine to the level recommended by Rose, or adding pyridoxine was studied on the growth depression, caused by methionine excess in the diet of rats. Lysine improved food consumption and weight gain, showing an average of 23.5g for the two-week period, while it was 17.5g on the methionine excess diet. However, it did not reach the 35g of the basal diet group Both histidine and pyridoxine did not have any effect, the liver weight changes of rats were related to their body weight changes. No significant differences in liver nitrogen, liver water content and concentration of hemoglobin among the different groups were found.

Fifty four male Wistar rats weighing 60-90g were divided into three groups of 18 each; rice-soybean basal diet with 0.2%DL-methionine as control, 2.0%D1-methionine supplemented group, 2.0%DL-methionine and 3.0%glycine supplemented group. All animals were housed in individual wire cages and both experimental diet and water were given ad libitum. After feeding 21 days, 0.037MBq/g bw of 3H-leucine was injected intraperitoneally. At 1,2, 4, 6, 8, 10 hours after injection, three rats per group were killed and the radioactivity of 3H-leucine per mg hepatic and brain tissue (dpm/mg tissue) were determined by liquid scintillation counter. The results showed that 3H-leuciue incorporarted during the entire 10 hours period of observation markedly declined and its peak was delayed in the hepatic tissue of excessive methionine supplemented group. However, 3H-leucine incorporated was improved significantly in liver in the rats fed excessive DL-methionine with glycine diet. In contrast, no significant difference of incorporation in the rat brain among the three groups were found. The results demonstrated that the addition of excess methionine retarded evidently protein synthesis of hepatocytes in the rats, but no similar toxic effect occurred in the rat brain tissue.