Inhibition of early resistance exercise‐induced translational signaling attenuates the sustained increase in protein synthesis rate 24 hours later

Fischer 344 x Brown Norway male rats (8 mo, n=7/group) were subjected to 10 sets of 6 resisted maximal lengthening contractions by unilateral high‐frequency (100 Hz) electrical stimulation of the sciatic nerve. Rats were subcutaneously injected with saline (SAL) or AICAR [an activator of the translational signaling inhibitor 5′‐AMP‐activated protein kinase (AMPK)] 40 min prior to exercise. Exercised and resting contralateral control tibialis anterior (TA) muscles were removed 20 min or 24 hours post‐exercise. At 20 min, western blotting revealed a greater (p ≤ 0.05) contraction‐induced phosphorylation response in SAL vs. AICAR muscles for p70 S6k (Thr 389 ), p90 RSK1 (Ser 380 ), and eukaryotic elongation factor 2 kinase (eEF2k; at Ser 366 , an inhibitory site). AICAR eliminated the contraction‐induced dephosphorylation of eEF2 at Thr 56 (an inhibitory site). As hypothesized, contraction increased 24‐hr post‐exercise protein synthesis rate ( 3 H‐Phe) in SAL but not AICAR. At 24 hours, p70 S6k phosphorylation was increased and total eEF2k protein content (an eEF2 inhibitor) was decreased by contraction in both SAL and AICAR. However, no differences were observed for eEF2 in any treatment condition at this timepoint. Thus, early exercise‐induced translational signaling may be important for the sustained increase in protein synthesis rate 24 hours post‐resistance exercise. (Supported by NIH AG025101)