The dynamics of synthesis and degradation of polyamines in normal and regenerating rat liver and brain.

Putrescine (1,4-diaminobutane), the product of the decarboxylation of ornithine, is a precursor of the polyamines spermidine and spermine. After administration in uiuo of radiolabeled ornithine or putrescine, changes in specific activity of putrescine, spermidine, and spermine have been assessed in normal and regenerating liver and in brain. In both normal liver and in brain, after labeling with exogenous putrescine, the specific activity of spermidine declines with a half-life of about 4 days. Following partial hepatectomy, marked and characteristic changes occur in the endogenous levels of putrescine, spermidine, and spermine in the regenerating liver of the rat. Putrescine concentration is increased S-fold as early as 4 hours after the operation, whereas spermidine levels rise more slowly and attain a maximum which is double that of control values within the first 5 days. Spermine concentration declines initially but becomes elevated by 11 days after hepatectomy. In regenerating rat liver, the rate of decline of the labeling of spermidine after administration of 14C-putrescine or 14C-ornithine is the same as in normal liver. There is a very rapid fall (1: = 2 hours) of the labeling of putrescine in regenerating rat liver after the administration of 14C-ornithine.