Initiating treadmill training in late middle age offers modest adaptations in Ca handling but enhances oxidative damage in senescent rat skeletal muscle

Thomas MM, Vigna C, Betik AC, Tupling AR, Hepple RT. Initiating treadmill training in late middle age offers modest adaptations in Ca handling but enhances oxidative damage in senescent rat skeletal muscle. Am J Physiol Regul Integr Comp Physiol 298: R1269–R1278, 2010. First published March 3, 2010; doi:10.1152/ajpregu.00663.2009.— Aging skeletal muscle shows an increased time to peak force and relaxation and a decreased specific force, all of which could relate to changes in muscle Ca handling. The purpose of this study was to determine if Ca -handling protein content and function are decreased in senescent gastrocnemius muscle and if initiating a training program in late middle age (LMA, 29 mo old) could improve function in senescent (34to 36-mo-old) muscle. LMA male Fischer 344 Brown-Norway rats underwent 5–7 mo of treadmill training. Aging resulted in a decrease in maximal sarco(endo)plasmic reticulum Ca ATPase (SERCA) activity and a decrease in Ca release rate but no change in Ca uptake rate. Efficiency of the Ca pump was increased with age, as was the content of SERCA2a. Training caused a further increase in SERCA2a content. Aging also caused an increase in protein carbonyl and reactive nitrogen species damage accumulation, and both further increased with training. Consistent with the increase in oxidative damage, heat shock protein 70 content was increased with age and further increased with training. Together, these results suggest that while initiating exercise training in LMA augments the age-related increase in expression of heat shock protein 70 and the more efficient SERCA2a isoform, it did not prevent the decrease in SERCA activity and exacerbated oxidative damage in senescent gastrocnemius muscle.