Electromyostimulation with blood flow restriction enhances activation of mTOR and MAPK signaling pathways in rat gastrocnemius muscles.

Neuromuscular electrical stimulation (NMES) combined with blood flow restriction (BFR) induces muscle hypertrophy. However, cellular mechanisms underlying the muscle hypertrophy induced by NMES combined with BFR remain unclear. We tested the hypothesis that NMES combined with BFR would enhance the mechanistic target of rapamycin (mTOR) and mitogen activated protein kinase (MAPK) signaling pathways. Age-matched male Wistar rats (6 months old, n=7 per group) were assigned randomly into control, BFR alone (BFR), NMES alone (NMES) and NMES combined with BFR (NMES/BFR) groups. NMES induced 25 isometric contractions lasting 8 s with a 4-s resting period between each contraction in the gastrocnemius muscle. Four sets in total were performed, with 1-min intervals between each set. A latex cuff was placed on the proximal portion of the hind limb and blood flow restriction at 200 mmHg was conducted in four sets (each set 5 min) with 1-min rest intervals between sets. Venous blood was collected from the lateral tail vein to determine pH, H+, and lactate, before and immediately after the treatments. Expression levels of proteins related to muscle hypertrophy were determined by western blot analysis. The application of NMES combined with BFR encouraged muscle fatigue more than NMES alone. NMES/BFR induced greater changes in accumulation of metabolites and increase in the weight of gastrocnemius muscle. The phosphorylation of mTOR and MAPK signaling related proteins was also enhanced following NMES combined with BFR, compared with other conditions. Thus, NMES enhanced the activation of mTOR and MAPK signaling pathways when combined with BFR.