Temporal changes of [3H]uridine and [14C]thymidine incorporation and total organ DNA and RNA in rat thymus.

Aging at organ, cell and molecular levels is characterized by a variety of deleterious changes. Theoretically, all of these changes must be linked to the primary informational molecule DNA and its ancillary control proteins. The present experiments were done to determine how the rate of nucleotide uptake and/or total quantity of RNA and DNA vary with age. Thymus showed age-related changes in radionucleotide uptake and total quantity of RNA and DNA. The ratio of DNA to RNA is higher in organs of younger animals. Total organ thymus DNA decreased between maturity and senescence. Sexual maturation correlates with DNA and RNA in total organ content or in synthesis.