General and Regional Turnover of Ribosomal Ribonucleic Acids in the Brain of Male and Female Rats during Postnatal Development

The turnover rates of brain rRNAs were measured in male and female Wistar rats during the postnatal (7–31 days) and “adolescent” (38–58 days) periods in either the whole hemispheres or in the various substructures. These rates were considerably accelerated during the postnatal development, with T/2 values being reduced by 50 percent or more in the adult rats (26) when compared to the younger group. A difference in rRNA replacement rates was observed throughout the postnatal life between males and females. It was moderately significant in the younger group and highly significant in adolescents and young adults. These differences were also demonstrable in most of the studied cerebral substructures. The growth-correlated and sex-linked differences found are discussed in terms of RNA conservation as related to growth rate, the evolving male and female sexual steroid patterns, and the possible sexual dimorphism unrelated to sex hormones.