Age-related decline in ligand-induced actin polymerization in human leukocytes and platelets

Abstract

The change in monomeric actin was measured in human polymorphonuclear leukocytes (PMN) and platelets, using the DNase I inhibition assay, after stimulation with various agents. PMN were stimulated with the chemotactic peptide n-formyl-methionyl-leucyl-phenylalanine (FMLP) in 199 donors, the tumor promoter phorbol myristate acetate in 112 donors, and the hormones tri-iodothyronine and phenylephrine, in 118 donors. The donors ranged in age from 20 to 89 years. A decrease in ligand-induced actin polymerization was detected in PMN obtained from the older population, on stimulation with FMLP (p = .014) and PMA (p = .0038). In platelets stimulated with thrombin (163 donors) a significant decrease in actin polymerization also was noted in the older group (p = .017). In addition, in platelets actin polymerization was less in women compared with men (p = .042). Because actin polymerization is an event that might have an important role in cellular activation, the age-related decline in the physiological functions might be related to a decrease in ligand-induced actin polymerization.