title: Chemical energetics of slow- and fast-twitch muscles of the mouse.
abstract: The energy utilization associated with contraction was measured in isolated slow- and fast-twitch muscles of the mouse at 20 degrees C. The extent of this utilization was estimated from either the extent of high-energy phosphate splitting occurring during contraction (the initial chemical change, delta approximately P init) or from the extent of recovery resynthesis calculated from the observed oxygen consumption and lactate production occurring during the recovery period (recovery chemical resynthesis, delta approximately P rec). For short tetani, the cost to maintain isometric tension in the fast-twitch extensor digitorum longus (EDL) was approximately threefold greater than that in the slow-twitch soleus. With prolonged stimulation, however, the energy cost in the EDL diminished so that after 12 s of stimulation, the energy cost in the EDL was only 50% greater than that of the soleus. For both the slow-twitch soleus and the fast-twitch EDL and for all tetanus durations (up to 15 s), the extent of the initial chemical change was identical with the amount of recovery chemical resynthesis, showing that a biochemical energy balance existed in these muscles.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003080:Cold Temperature; D004734:Energy Metabolism; D066298:In Vitro Techniques; D008297:Male; D008433:Mathematics; D051379:Mice; D009119:Muscle Contraction; D009132:Muscles / Q000378:metabolism*; D010101:Oxygen Consumption
chemical_list: D000255:Adenosine Triphosphate