We previously demonstrated increased fatigability in vitro of masseter muscles from male and female rats with advancing age. The goal of the present experiments was to determine if this loss of endurance is associated with decreased activity of enzymes involved in energy metabolism. Male and female Fischer 344 rats were obtained from the Harlan-NIA colony at ages 6, 12, 18 and 24 months. Masseter muscle enzyme activities were measured at 30°C using muscle homogenates prepared in 175 mM KCl containing 10 mM Tris-HCl and 2 mM EDTA at pH 7.2. Cytochrome oxidase, citrate synthase and succinate dehydrogenase levels served as indices oxidative capacity. Lactate dehydrogenase and phosphorylase activities were used to assess glycolyuc potential. Carnitine palmitoyl-transferase and 3-hydroxyacyl CoA dehydrogenase activities were used to assess capacity for fatty acid oxidation. Only citrate synthase activity correlated with the observed decrease in endurance of muscles from male and female rats. We conclude that the supply of energy in fatiguing contractions of masseter muscles of elderly rats may be rate-limited by citrate synthase enzyme activity.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology