Polyamine acetylation in the developing and aging mouse brain

Putrescine and spermidine acetylation is at least 10‐fold higher in the brain homogenate of the neonate (1‐day‐old) mouse than in the adult (90 days old). Although the pattern of putrescine and spermidine acetylation is similar throughout development, the acetylation of spermidine is consistently higher. As the animal matures, the activity curves tend to converge. In the P 1 (crude nuclei) and microsomal fractions, the acetylation of spermidine is highest at day 1, while putrescine acetylation peaks at day 4. In contrast to the adult animal, putrescine and spermidine acetylation are present in the P 2 (crude mitochondria) and soluble fractions. In the P 2 fraction, spermidine acetylation is highest at birth, while the acetylation of putrescine peaks at day 3. Acetylation of both substrates is barely detectable by day 42. In the soluble fraction, putrescine and spermidine acetylation show the highest activity at day 5. The activity declined towards adult values by day 10 in all the fractions examined. Acetylation of putrescine and spermidine is approximately 4‐fold higher in the brain homogenate of the 120‐day‐old mouse than in that of the 90‐day‐old mouse. Both the acetylation of putrescine and spermidine decline as the animal grows older. In contrast to the perinatal period (day 20 of gestation to 4 days old) the acetylation of putrescine is almost identical to that of spermidine in the adult mouse. These results suggest that polyamine acetylation may play an important role in polyamine metabolism in the developing mouse brain. The presence of activity in the P 2 and soluble fractions of the neonatal, but not adult mouse brain, suggests that putrescine, via acetylputrescine, may contribute to the GABA levels during development.