title: O2 occlusion and cyanide induced immediate relaxation and contraction of murine skeletal muscle.
abstract: The acute changes of muscle tone and membrane current upon occlusion of oxygenation (O2 occlusion) were studied in vitro in mouse diaphragms. O2 occlusion immediately produced a contraction and a relaxation, respectively, in ryanodine- and high K(+)-contracted muscles while a biphasic change (an initial decrease then a late increase) of muscle tone was produced in muscles contracted with caffeine. The O2 occlusion effects were reversed after reoxygenation. CN- produced similar acute changes of muscle tone and abolished O2 occlusion effects. The O2 occlusion-induced relaxation in high K+ medium was converted into a contraction by 3,4-diaminopyridine and by low Cl- Tyrode's. O2 occlusion induced a small outward current and membrane hyperpolarization at a rate slower than the changes of muscle tone. Glybenclamide inhibited all of the changes induced by O2 occlusion. It is possible that the K+ and Cl- permeabilities of sarcoplasmic reticulum are highly sensitive to hypoxic challenge and related to the immediate changes of muscle tone after O2 occlusion.
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, ROC.
authors.forename: S J
authors.initials: SJ
authors.lastname: Hong
authors.forename: C C
authors.initials: CC
authors.lastname: Chang
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D003486:Cyanides / Q000494:pharmacology*; D004558:Electric Stimulation; D005905:Glyburide / Q000494:pharmacology; D000860:Hypoxia / Q000503:physiopathology*; D066298:In Vitro Techniques; D051379:Mice; D008813:Mice, Inbred ICR; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000494:pharmacology; D012132:Respiratory Muscles / Q000187:drug effects* / Q000502:physiology*; D012433:Ryanodine / Q000494:pharmacology; D012964:Sodium / Q000502:physiology
chemical_list: D003486:Cyanides; D012433:Ryanodine; D002110:Caffeine; D012964:Sodium; D011188:Potassium; D005905:Glyburide