Iodoacetate-induced contracture in rat skeletal muscle: possible role of ADP.
The effects of iodoacetic acid (IAA) and ischemic contraction were studied in rat extensor digitorum longus muscles. Ischemic contraction of IAA-treated muscles produced contracture. The onset of contracture was not associated with a change in sarcolemmal electrical properties or reduction in intracellular [ATP]; however, [creatine phosphate] was reduced by 75% and free [ADP] was increased by 665%. Continued stimulation of IAA-treated fibers resulted in depolarization, loss of membrane excitability, further depletion of creatine phosphate, and reduction in [ATP]. The effects seen in IAA-treated muscle did not appear to result from a direct action of IAA on the surface membrane, contractile proteins, or excitation-contraction coupling. The contractures in IAA-treated muscle may have resulted from increased Ca sensitivity of the contractile proteins, increased myoplasmic [Ca], or both. Both effects may have resulted from increased [ADP]. In addition, the reduced acidification during ischemic contraction of IAA-treated fibers compared with control fibers may have further increased the Ca sensitivity of IAA-treated fibers compared with controls.
Ruff
R L
RL
Department of Neurology, Cleveland Veterans Affairs Medical Center, Ohio 44106.
Weissman
J
J
D000244:Adenosine Diphosphate / Q000502:physiology*; D000818:Animals; D004056:Differential Threshold; D004558:Electric Stimulation; D006652:Histological Techniques; D007461:Iodoacetates / Q000494:pharmacology*; D019807:Iodoacetic Acid; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010710:Phosphates / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D007461:Iodoacetates; D010710:Phosphates; D000244:Adenosine Diphosphate; D019807:Iodoacetic Acid