title: In vitro muscle contracture investigations on the malignant hyperthermia like episodes in myotonia congenita.
abstract: BACKGROUND
  A common form of congenital myotonia, myotonia congenita (MC), is caused by mutations in the skeletal muscle Cl(-) channel gene type 1 (CLCN1). Due to the reduced Cl(-) conductance of the mutated channels, the patients may develop generalized muscle rigidity and hypermetabolism during general anaesthesia. The clinical symptoms resemble malignant hyperthermia (MH), which may lead to mistreatment of the patient.
  
  
  METHODS
  Muscle specimens of ADR mice (an animal model of MC) as well as of human individuals were used and exposed to potent ryanodine receptor type 1 (RyR1) activators and increasing K(+) concentration. Muscle force was monitored by a standardized diagnostic method for MH, the so-called in vitro contracture test.
  
  
  RESULTS
  Neither muscle of ADR mice nor MC muscle (murine and human myotonic muscle) showed pathological contractures after exposure to the potent RyR1 agonists caffeine and halothane. Increasing concentrations of K(+) had a dose-dependent preventive effect on myotonic stiffness.
  
  
  CONCLUSIONS
  We conclude that the adverse anaesthetic MH-like episodes observed in MC patients do not primarily originate from an altered Ca(2+) release in skeletal muscle. In MC muscle, this hypermetabolism is facilitated by a (pharmacologically induced) sustained depolarization due to an instable membrane potential. The in vitro results suggest that these patients benefit from tight K(+) monitoring because of the membrane potential stabilizing effect of K(+) .
authors: Department of Anaesthesiology, Ulm University, Ulm, Germany.
authors: K
authors: K
authors: Hoppe
authors: F
authors: F
authors: Lehmann-Horn
authors: S
authors: S
authors: Chaiklieng
authors: K
authors: K
authors: Jurkat-Rott
authors: O
authors: O
authors: Adolph
authors: W
authors: W
authors: Klingler
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006221:Halothane / Q000494:pharmacology; D066298:In Vitro Techniques; D008305:Malignant Hyperthermia / Q000503:physiopathology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008818:Mice, Neurologic Mutants; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D009224:Myotonia Congenita / Q000503:physiopathology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects
chemical_list: D018685:Anesthetics, Inhalation; D000697:Central Nervous System Stimulants; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D002118:Calcium; D006221:Halothane