Protein turnover and growth of the rat brain from the foetus to old age.

Growth of the rat brain was studied between 16 days of foetal life and old age (105 weeks). Developmental changes in cerebral RNA, DNA, and protein contents are described. The age-related decline in brain growth rates correlates with progressive decreases in the fractional rates of protein synthesis (from 58 to 6.8% per day) and breakdown (from 36.4 to 4.1% per day).