Age-related changes in cAMP and cGMP levels during phagocytosis in human polymorphonuclear leukocytes

Alterations of cyclic nucleotides have been studied during the incorporation of opsonized yeast cells into human polymorphonuclear leukocytes (PMNL) from both young and aged subjects. In PMNLs obtained from healthy young males the cAMP level rose to a maximal value during the first 15 min and returned to the starting level at the 60th min of phagocytosis. The cGMP level started to rise only at the 30th min of incorporation and enhanced progressively up to the 120th min. In contrast, the elevated cAMP level remained increased during the 120 min of phagocytosis in PMNLs obtained from aged subjects, whereas the cGMP level was not altered during the same period. The basic level of cAMP diminished, while the cGMP level was found to be elevated with ageing in PMNLs. It is concluded that phagocytosis was not impaired with age yet cytotoxic functions were diminished and that the data presented support the idea that cyclic nucleotides may be directly involved only in the latter process.