DIFFERENT TURNOVER RATES OF BRAIN RIBOSOMAL RIBONUCLEIC ACIDS IN MALE AND FEMALE RATS

— Following a single intracranial injection of [5-3H]orotic acid, the decay dynamics were determined for rRNAs of whole brain in male and female Wistar-inbred albino rats aged 2.5-3.5 months. The turnover rate for male brain rRNAs was significantly lower than in females (mean half-lives being, respectively, 12.2 ± 2.2 (S.D.M.) days, and 7.4 ± 1.3 days in four regression measurements). This difference was apparently not related to the turnover rate of acid-soluble brain nucleotides, which turned over much faster and at a similar rate in rats of both sexes; it also could not be connected with brain levels of rRNAs or DNAs, which were quite similar For males and females. The results are discussed in terms of possible sex hormone determination of brain RNA metabolic patterns especially in males.