Stress due to endurance training of striated
muscles leads to adaptive changes in the distribution of
muscle fiber types (i.e. ratio of type I and type II fibers). Moreover, severe training leads to tissue hypoxia and oxidative stress in
muscles. In the current study, we exa
mined the relationship between histological changes and oxidative state in
muscles of
mastication during the acute adaptation phase to a sustained
muscle load. Six do
mestic pigs received build-ups on the
molar teeth in order to induce a sustained load of the
muscles of
mastication for a duration of four weeks. Afterwards the
masseter (M1, M2, M3),
medial pterygoid (PM), te
mporal (TP1, TP2), and geniohyoid
muscles (GH) were re
moved and the fiber type distribution was deter
mined by enzy
me histoche
mistry. Additionally, the tissue content of glutathione and lipid peroxidation (LPO) products were
measured. The above treat
ment led to
muscle fiber transfor
mation of type II into type I (M1, M2, TP2, PM) and a decrease of the GSH content (M1, M2 and TP2). The changes in the GSH/GSSG ratio were in accordance with the changes in proportions of
muscle fiber types, with the lowest GSH/GSSG ratios in the
most stressed
muscles of the treated ani
mals. No significant changes in LPO products were found.
The decrease of the GSH/GSSG ratio in the most stressed muscles indicates an increased intracellular oxidative stress, which may be caused by tissue hypoxia during the chronic phase of muscle adaptation.