Evidence for reversability of age-related decrease in human lymphocyte adenylate cyclase activity

Age-related loss of adenylate cyclase responsiveness to guanyl nucleotide was demonstrated in lymphocytes freshly isolated from human subjects. Enzyme activity of cells from young (<40 years) and elderly (>65 years) subjects were markedly sensitive to inhibition by non-ionic detergents. When enzyme activity in the presence of guanyl nucleotide and low concentrations of Triton X-100 was determined in a mixture of cells from the young and aged donors, the activity was 40±17 percent (mean ± S.D.) greater than anticipated from the activity of the cells of the two age groups assayed separately. The detergent range which facilitated the enhanced enzyme activity was too low to extract the catalytic subunit of adenylate cyclase from the cells. These results further suggest that in man, changes distal to receptors contribute to diminished responsiveness of lymphocyte adenylate cyclase as a function of age. In addition, these age-related changes may be partially reversible by reconstitution with factors from cells from younger subjects.