Fig. 7. Rapid decrease in telomerase activity following exposure to oxidative stress. (A,B) Comparison between telomerase activity levels in HUVEC of the indicated replicative ages cultured under pro-oxidant (BSO) or normal conditions. (A) TRAP products (50 base pairs); IC, internal polymerase chain reaction control in the TRAP assay. (B) Relative telomerase activity levels corresponding to the blots shown in A. (C) Time course of telomerase activity in young HUVEC (6 CPD) following a single exposure to 10 µM BSO. Values represent the mean (± s.d.) of duplicate cultures from representative experiments. (D) Immunoblots showing levels of hTERT in nuclear extracts at the indicated time points after the initial oxidant treatment at passage 2 and 3.