Amino-acid enzyme activities in liver and kidney of developing rats

The amino-acid enzymes (aspartate-, alanine- and tyrosine transaminases, serine dehydratase, glutamate dehydrogenase, glutamine synthetase, adenylate deaminase and arginase) activities in the liver and kidney of developing rats (days 19 and 21 after conception and 1, 5, 10, 20 and 30 after birth) compared with adults were determined in crude homogenates. Most enzymes attained the adult levels early after birth or at weaning, showing a marked trend towards amino-acid nitrogen conservation during late foetal and specially during the neonatal period, increasing their activity during lactation. It is postulated that these changes are closely related to availability of low grade protein in diet as well as to maturation of amino-acid homeostasis maintenance for growth.