Downregulation of telomerase in rat during the aging process

Telomerase is an RNA-dependent DNA polymerase that maintains the tandem arr ays of telomeric repeats at the eukaryotic chromosome ends. Because of its ability to replenish lost telomeric sequences, telomerase is thought to be required for cell proliferation. At present, very little information on the role of telomerase in aging is available. In the present study, we tested the telomerase activity of Fischer 344 rat testis and liver at 6, 12, 18 an d 24 months of age. As the testis is an androgen-dependent tissue, we also investigated the changes of testosterone and mRNA levels of androgen recept or in this tissue. Our results show that the telomerase activity of Fischer 344 rat testis significantly reduced at 24 months of age compared to 6 mon ths of age, and that the mRNA level of telomerase protein component 1 (TLP- 1) show a corresponding decrease with the telomerase activity. Interestingl y, this downregulation was not observed in the liver. The testosterone leve l in testis increased until 18 months of age, but reduced by 50% at 24 mont hs of age. Our conclusions are that the telomerase activity is age-dependen t and its change is a tissue-specific phenomenon.