Age-related variation in the DNA-repair synthesis after UV-C irradiation in unstimulated lymphocytes of healthy blood donors.

UV-C light-induced DNA-repair synthesis was studied in unstimulated lymphocytes of 51 healthy blood donors aged between 17 and 74 years. Repair synthesis was measured by the incorporation of [3H]thymidine after a 2-h incubation period in the presence of 2 mM hydroxyurea. The evaluation included (1) the spontaneous DNA-synthesis in unirradiated lymphocytes with and without hydroxyurea, (2) the DNA-repair synthesis in lymphocytes irradiated with UV-light. The interindividual variation was significantly higher than the methodological variation ascertained in 24 persons in whom 2 determinations were carried out. In blood donors aged between 17 and 39 years, the spontaneous DNA synthesis, both with and without hydroxyurea, was significantly lower than in older individuals. The DNA-repair synthesis was dependent on the dose of UV-C light between 2 and 16 J/m2. There were no significant differences in DNA-repair synthesis in the age range 17-74 years. The variations in rate of DNA-repair synthesis (greater or lesser degree of [3H]thymidine incorporation beyond the 99% confidence range) were wider in older (44-74 years), than in younger individuals.