Table 1.

Repair of AP sites in old and young IMR90 cells

Senescent [population-doubling levels (PDLs) 46-54] and young (PDLs 25–30) IMR90 cells (2 × 10⁶/ml in DMEM supplemented only with 25 mM Hepes) were treated with a pulse of 10 mM hydrogen peroxide for 5 min at 37°C and incubated for recovery. Immediately after, and at 15-min intervals, aliquots were removed and AP sites were determined as described in Materials and Methods. The basal level of AP sites was determined in nontreated cells. *, P < 0.05; **, P < 0.01.  

^† Number of trapped AP sites/10⁶ nucleotides. The values are mean ± SE of at least five experiments.