Telomerase activity in cultured normal peripheral blood lymphocytes. (A) The kinetics of telomerase activity in normal cultured peripheral blood lymphocytes was determined in 2 separate experiments by measuring time-dependent changes in telomerase activity from 3 healthy donors. Each time point was measured in triplicate for each individual. Telomerase activity was absent upon collection, very low during the first day in vitro, significantly increased at day 2, and then slightly decreased over time until day 7. (B) Androgens activate telomerase activity of cultured lymphocytes. Methyltrienolone (R1881) induced telomerase function in a dose-dependent fashion (n = 10, 5 men and 5 women; each measurement done in triplicate; data are combined results from 3 different experiments). 19-nortestosterone (19-NT) also induced telomerase function but not 6β-hydroxy-testosterone (n = 2, in 2 experiments; *P < .05; ***P < .001).