title: Detection of proton release from cultured human myotubes to identify malignant hyperthermia susceptibility.
abstract: BACKGROUND
  Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle. During general anesthesia, a life-threatening hypermetabolic state may occur resulting from increased release of Ca2+ from the sarcoplasmic reticulum in skeletal muscle. Diagnosis of MH susceptibility requires surgical muscle biopsies to measure force in response to chemical stimulation (in vitro contracture test, IVCT). Here, the authors investigated an alternative way of discriminating MH-susceptible (MHS) from normal (MHN) subjects by using cultured human myotubes and measuring proton release as an indicator of cellular metabolism.
  
  
  METHODS
  Myotubes were stimulated with the Ca2+ release channel agonist 4-chloro-m-cresol (4-CmC), leading to metabolic activation and proton secretion. The rate of extracellular acidification was recorded with a silicon sensor chip.
  
  
  RESULTS
  A stepwise increase in 4-CmC concentration led to a phasic-tonic increase in the acidification rate. The response, measured at different concentrations of 4-CmC, was considerably larger in cultures from MHS compared with MHN subjects and correlated well with the force response in the IVCT.
  
  
  CONCLUSIONS
  The enhanced metabolism of cultured skeletal myotubes, likely originating from an increased myoplasmic Ca2+ concentration, can be monitored by studying the proton secretion rate. Because the method seems to be able to distinguish normal from pathologic phenotypes, it is a promising technique for possible future use in less invasive MH testing.
authors.affiliation: Department of Anesthesiology, University of Ulm, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Klingler
authors.forename: Christoph
authors.initials: C
authors.lastname: Baur
authors.forename: Michael
authors.initials: M
authors.lastname: Georgieff
authors.forename: Frank
authors.initials: F
authors.lastname: Lehmann-Horn
authors.forename: Werner
authors.initials: W
authors.lastname: Melzer
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003408:Cresols; D004198:Disease Susceptibility; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008305:Malignant Hyperthermia / Q000175:diagnosis* / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D011522:Protons
chemical_list: D003408:Cresols; D011522:Protons; C006984:chlorocresol; D002118:Calcium