Study of Essential Amino Acid Requirement on the Basis of Sulfur Amino Acid Metabolism in Young Rats

抄録

Requirement of essential amino acid for growing rats was examined on the basis of hepatic cysteine dioxygenase (CDO) activity, hepatic glutathione, cysteine and taurine contents and urinary taurine excretion.

Young male rats were fed on the semipurified diets limited by sulfur amino acids (methionine+cystine) in the levels of 0.20, 0.30, 0.45, 0.50, 0.55 and 0.60% of requirement recomended by NRC for 18 days. The values hepatic glutathione, cysteine and taurine of 0.50% limitation of sulfur amino acid level were similar to those of controls (0.60% ). The values of CDO activity and urinary taurine excretion increased in animals fed on 0.55% limitation of sulfur amino acids diets, and the values showed very low less than 0.45% limitation. It is estimated that level of 0.49% (about 0.50%) limitation of sulfur amino acid meet the minimum requirement. Requirements of lysine and threonine were also studied in animals fed on 0.45% limitation of sulfur amino acids and different level of each test amino acids. Hepatic glutathione, CDO activity and urinary taurine were also used as parameters. It was estimated minimum requirements of lysine and threonine are 0.61-0.66% limitation, and 0.42-0.48% limitation, respectively.