Effects of chronic overload on muscle hypertrophy and mTOR signaling in young adult and aged rats

Abstract

We examined the effect of 28 days of overload on mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) signaling in young adult (Y; 6-month old) and aged (O; 30-month old) Fischer 344 × Brown Norway rats subjected to bilateral synergist ablation (SA) of two thirds of the gastrocnemius muscle or sham surgery (CON). Although plantaris (PLA) muscle hypertrophy was attenuated by aging, mTOR phosphorylation was 44% and 35% greater in Y SA and O SA compared with CON (p =. 038). Ribosomal protein S6 phosphorylation was 114% and 24% higher in Y SA and O SA compared with CON (p =. 009). Eukaryotic initiation factor 2Bε phosphorylation was 33% and 9% higher in Y SA and O SA compared with CON (p =. 04). Translational signaling in young adult and aged plantaris muscle is equally responsive to chronic overload. The Author 2009. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org.2009 © The Author 2009. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org.