TELOMERIC LENGTH AND TELOMERASE ACTIVITY VARY WITH AGE IN PERIPHERAL-BLOOD CELLS OBTAINED FROM NORMAL INDIVIDUALS

The telomerase activity and length of telomeres of peripheral blood mo nonuclear cells obtained from 124 healthy individuals aged 4-95 years was measured. Telomerase activity level was semiquantitatively assesse d by a fluorescent-telomeric repeat amplification protocol (fluorescen t-TRAP) using an internal telomerase assay standard, fluorescent prime rs and an automated laser fluorescent DNA sequencer. Telomeric length, measured by assay of terminal restriction fragments (TRFs), was deter mined in HinfI-digested DNA by Southern blot analysis using a (TTAGGG) (4) probe. TRF length was determined in 80 individuals and age-related progressive reduction of size was observed. TRF length in peripheral blood mononuclear cells obtained from normal individuals (aged 4-39 ye ars) decreased by approximately 84 bp per year, while in individuals a ged greater than or equal to 40 years it decreased by 41 bp per year. In contrast, telomerase activity showed an apparent biphasic pattern w ith aging. Individuals aged 4-39 years showed a progressive decrease i n telomerase activity, whereas 65% of those aged greater than or equal to 40 years showed relatively stable but very low telomerase activity , and the remaining individuals aged greater than or equal to 40 years had no detectable telomerase activity.