Development changes of polyamine biosynthesis in rat liver.

To investigate the role of polyamine metabolism in fetal development, we determined the hepatic polyamine content and the activity of enzymes related to polyamine metabolism in fetal, newborn and adult rats. In the fetuses, spermidine was detected at the highest level, followed by spermine and then putrescine. Putrescine and spermidine levels were higher in the fetuses than in adult rats, while the spermine level was significantly lower in the fetuses. The activities of the enzymes investigated were also higher in the fetuses than in adult rats. These findings indicate that polyamine synthesis was enhanced in the fetal liver, and that degradation of spermidine via spermidine N1-acetyltransferase contributes to the increase in putrescine levels. Thus, our study suggests that an increase in putrescine is important for fetal growth and that putrescine per se has a significant role in fetal cellular proliferation.