Age-related decreases in lymphocyte protein kinase C activity and translocation are reduced by aerobic fitness

This study investigated the effects of advancing age and long-term aerobic fitness on lymphocyte protein kinase C (PKC) activity and translocation. Lymphocytes were obtained from young (20-36 years old) and older (61-78 years old) healthy men who were either aerobically conditioned or deconditioned. Both baseline PKC activity and the response of this enzyme to the direct PKC stimulating agent, phorbol 12-myristate, 13-acetate (PMA) or to the mitogen, phytohaemagglutinin (PHA), were measured in partially purified extracts of cytosolic and membranous fractions of lymphocytes. Basal PKC activity, PMA-induced redistribution of PKC, and PHA-induced enhancement of PKC activity were reduced among older subjects in both lymphocyte cytosolic and membranous fractions. However, the magnitudes of these reductions were smaller among the older subjects who were aerobically fit. Lymphocyte PKC activity and translocation may be biological markers of aging, and the maintenance of aerobic fitness into later life may serve to slow the rate at which activation of this enzyme declines during senescence.