Aging increases the oxidation of dichlorohydrofluorescein in single isolated skeletal muscle fibers at rest, but not during contractions

Abstract

[EN] An in-crease in the activity of reactive oxygen species (ROS) has beenimplicated in the mechanisms of loss of skeletal muscle that occursduring aging, but few studies have attempted to directly assessactivities in intact muscle fibers. The current project used the nonspe-cific fluorescent probe for ROS and reactive nitrogen species, 5-(and-6)-chloromethyl-2=,7=-dichlorodihydrofluorescein (CM-DCFH), insingle, isolated, mature skeletal muscle fibers from adult and old micein addition to biochemical measurements of key regulatory proteinsfor ROS in muscles of these animals. Data confirmed the changes inkey regulatory processes for ROS (increased glutathione peroxidase 1and catalase activities and reduced total glutathione content) previ-ously reported in muscle from old mice and showed increased CM-DCFH oxidation in muscle fibers from old mice at rest and indicatethat these changes are likely due to an increase in generation ofoxidants rather than a lack of scavenging capacity. The increasedCM-DCFH oxidation persisted even when cellular defenses againstoxidants were increased by loading fibers from young and old micewith glutathione. During contractile activity, and in contrast to theincrease observed in fibers from young mice, there was no furtherincrease in CM-DCFH oxidation in muscle fibers from old mice.These data also suggest that the defect in short-term adaptations tocontractions that occurs in old mice may be related to a diminished, orabsent, increase in the muscle generation of ROS and/or reactivenitrogen species that normally accompanies contractile activity inyoung mice.