Changes in pH with age in Drosophila and the influence of buffers on longevity.

The pH of whole homogenates of Drosophila melanogaster declines from 7.44 during the first instar larval stage to 6.77 during the late pupal stage. In adult flies the pH declines from 6.92 to 6.70 with increasing age. Total carbonic anhydrase activity declines during the first 10 days of the adult stage. The carbonic anhydrase inhibitor acetazolamide failed to shorten life span. Low molecular weight buffers prolong the median life span when fed to flies in the pH range 7.0-8.3. The greatest prolongation occurs when the flies are given the buffers beginning at 2 weeks of age. 0.1 M HEPES (pH 7.5) increased life span by 22.9% and 0.01 M KHCO3 (pH 7.0) by 17.8%.