Enzyme regulation during development and aging.

Glutamine synthetase and ornithine aminotransferase activities have been shown to decrease in aging rats, but the decline varies in degree for the two enzymes in liver and kidney. The responsiveness of the two liver enzymes to glucagon and cyclic AMP demonstrates a similarity in enzyme regulation between developing and aging rats and a contrast in enzyme regulation between these animals and young adults. The results are interpreted as showing a reversion in certain aspects of enzyme regulation during aging to those prevailing in the perinatal state.