title: Effects of 2-n-butyl-methylenedioxyindene on skeletal muscle mechanics and energetics.
abstract: Mechanical and energetic effects of 2-n-butyl-3-dimethylamino-5,6-methylenedioxyindene (2-butyl-MDI) were investigated in isolated frog semitendinosus muscles at 0 degrees C. Previous research on various tissues suggested that this compound functions as an intracellular Ca2+ antagonist. The effects of 2-butyl-MDI (2 X 10(-4) M) with respect to time were progressive and reversible with exposures of 30 min or less. A 30-min exposure to the agent significantly decreased twitch and tetanus force and energy liberation, increased the twitch-to-tetanus ratio, prolonged kinetics of force development, induced a stimulus frequency-dependent tetanic fatigue, and decreased contractile economy (measured as force per unit energy liberation). Energy associated with Ca2+ cycling, activation heat, was depressed by 31 +/- 4%. The significant reduction of activation heat production by 2-butyl-MDI suggests that the quantity of Ca2+ released by the sarcoplasmic reticulum upon stimulation is reduced. However, the complexity of the results summarized above suggests multiple sites and/or modes of action for the agent.
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001833:Body Temperature Regulation; D004734:Energy Metabolism / Q000187:drug effects*; D005260:Female; D006614:Hindlimb; D007192:Indenes / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000502:physiology*; D011894:Rana pipiens
chemical_list: D007192:Indenes; C027984:2-n-butyl-3-(dimethylamino)-5,6-methylenedioxyindene