DECREASED RATES OF CA2-DEPENDENT HEAT-PRODUCTION IN SLOW-TWITCH AND FAST-TWITCH MUSCLES FROM THE DYSTROPHIC (MDX) MOUSE()

Using a newly developed microcalorimetric approach to assess the rate of energy expenditure for intracellular [Ca2+] homeostasis in isolated muscles at rest, we found this was lower in mdx than in control mouse muscles, by 62% and 29% in soleus and extensor digitorum longus, resp ectively. Differences in total and Ca2+-dependent rates of specific he at production between mdx and control were enhanced during sustained, KCl-induced stimulation of energy dissipation. These results suggest t hat the low sacroplasmic energy status of dystrophic muscles is not du e to any excessive energy expenditure for intracellular [Ca2+] homeost asis.