Polyamine metabolism in liver of young rats

Abstract
Rat liver undergoes a phase of rapid growth during weaning. The changes in polyamine metabolism occurring during this period of natural growth were followed and compared with changes in DNA and RNA accumulation. There was a 2.5-fold increase in the number of cells/liver between suckling (18-19 days old) and weanling (30-32 days old) rats. Ornithine decarboxylase [EC 4.1.1.17] activity increased from the low value in 18 day old rat pups and remained significantly higher (approximately 5- to 10-fold) than that in adult rats from day 21 to day 34. Putrescine-dependent S-adenosylmethionine decarboxylase [EC 4.1.1.50] activity was slightly but significantly increased during most of this period. Spermidine and RNA concentrations fluctuated in concert, whereas spermine content/cell doubled during the period from day 23-30.