title: Analysis of human cultured myotubes responses mediated by ryanodine receptor 1.
abstract: Malignant hyperthermia is a life-threatening condition caused by autosomal dominant mutations in the ryanodine receptor type 1 gene. Identifying patients predisposed to malignant hyperthermia is done through the Ca-induced Ca release test in Japan. We examined the intracellular calcium concentration in human cultured muscle cells and compared the sensitivity of myotubes to ryanodine receptor type 1 activators based on the Ca-induced Ca release rate. We assessed the utility of this method as an identifying test for predisposition to malignant hyperthermia. Muscle specimens were obtained from 34 individuals undergoing the Ca-induced Ca release test. We cultured myotubes from residual material and monitored changes in intracellular calcium concentration after exposure to the ryanodine receptor type 1 activators caffeine, halothane and 4-chloro-m-cresol by measuring fura-2 fluorescence. We determined the half maximal effective concentrations (EC50) for the test compounds in each myotube and calculated cut-off points using receiver operating characteristic curves. Seventeen patients each were classified into the accelerated and non-accelerated groups based on their Ca-induced Ca release rate. The EC50 values for caffeine, halothane and 4-chloro-m-cresol of the accelerated group were significant lower than those of the non-accelerated group (P < 0.001, P < 0.001 and P < 0.001, respectively). The calculated cut-off points of EC50 values for caffeine, halothane and 4-CmC were 3.62 mM, 2.28 mM and 197 microM, respectively. An increased sensitivity to ryanodine receptor type 1 activators was seen in myotubes in the accelerated group. This functional test on human cultured myotubes indicates that the alteration of their intracellular Ca2+ homeostasis may identify the predisposition to malignant hyperthermia.
authors.affiliation: Department of Anesthesiology and Critical Care, Hiroshima University, Hiroshima, Japan. petit88bois@sky.megaegg.ne.jp
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
authors.forename: K
authors.initials: K
authors.lastname: Mukaida
authors.forename: T
authors.initials: T
authors.lastname: Migita
authors.forename: H
authors.initials: H
authors.lastname: Hamada
authors.forename: M
authors.initials: M
authors.lastname: Kawamoto
authors.forename: O
authors.initials: O
authors.lastname: Yuge
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D003408:Cresols / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D020022:Genetic Predisposition to Disease; D006221:Halothane / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D008297:Male; D008305:Malignant Hyperthermia / Q000235:genetics*; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D012372:ROC Curve; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D055815:Young Adult
chemical_list: D003408:Cresols; D019837:Ryanodine Receptor Calcium Release Channel; C006984:chlorocresol; D002110:Caffeine; D002118:Calcium; D006221:Halothane