title: Recovery of action potentials and twitches after K-contractures in frog skeletal muscle.
abstract: To give information about intracellular Ca2+ translocation during and after K-contractures in vertebrate skeletal muscle fibers, we examined recovery of action potentials and twitches after interruption and spontaneous relaxation of K-contractures at low temperature (3 degrees C) that greatly reduced the rate of Ca2+ reuptake by the sarcoplasmic reticulum. On membrane repolarization interrupting K-contractures, the amplitude of both action potentials and twitches recovered quickly, while the falling phase of action potential was markedly slowed at first to prolong its refractory period, so that repetitive stimulation (20 Hz) did not produce a complete tetanus. Meanwhile, on membrane repolarization after spontaneous relaxation of K-contractures, the action potentials were markedly reduced in amplitude and prolonged in duration at first, also resulting in prolonged refractory period. These results are discussed in connection with Ca2+ absorption to the surface and transverse tubule membranes, producing changes in action potential kinetics.
authors.affiliation: Department of Physiology, School of Medicine, Teikyo University, Tokyo, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Suzuki
authors.forename: Ibuki
authors.initials: I
authors.lastname: Shirakawa
authors.forename: Kazunari
authors.initials: K
authors.lastname: Noguchi
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Kishi
authors.forename: Haruo
authors.initials: H
authors.lastname: Sugi
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004576:Electromyography; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011188:Potassium; D011898:Ranidae / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013696:Temperature
chemical_list: D011188:Potassium; D002118:Calcium