Gender and exercise regulate MAPKs following 1, 2 and 6 bouts of downhill running in murine skeletal muscle

Abstract

MAPKs (ERK1, ERK2, p38 and JNK) are part of the cellular stress response following exercise. Male and female mice (n=5) ran downhill (−15°) for 15 min for one, two or six bouts of exercise. The two bouts were separated by a week and the six bouts were completed every other day for three days followed by a two day rest. Following all three exercises, the MAPK activities showed striking gender and bout specific responses. The magnitude of these responses decreased with the number of bouts completed, likely due either to the repeated bout phenomenon or to the initiation of a hypertrophic program in the 2 and 6 bout protocols. Overall in all three exercise protocols, ERK1 and ERK2 activities showed a much more robust response to exercise than the SAPK’s, p38 and JNK, activities. Additionally, the females showed a greater magnitude response than did the males. Following six bouts of exercise, the myogenic markers cyclinD1 and PCNA, as well as citrate synthase, were markedly increased in expression or activity, suggesting satellite cell proliferation. The number of bouts demonstrated a clear, gender-specific remodelling of the MAPK activities, as well as a differentiation between the MAPKs and SAPKs.