Pharmacologic and functional characterization of malignant hyperthermia in the R163C RyR1 knock-in mouse.
BACKGROUND
Malignant hyperthermia is a pharmacogenetic disorder affecting humans, dogs, pigs, and horses. In the majority of human cases and all cases in animals, malignant hyperthermia has been associated with missense mutations in the skeletal ryanodine receptor (RyR1).


METHODS
The authors used a "knock-in" targeting vector to create mice carrying the RyR1 R163C malignant hyperthermia mutation.


RESULTS
Validation of this new mouse model of human malignant hyperthermia susceptibility includes (1) proof of transcription of the R163C allele and expression of ryanodine receptor protein in R163C heterozygous and R163C homozygous animals; (2) fulminant malignant hyperthermia episodes in R163C heterozygous mice after exposure to 1.25-1.75% halothane or an ambient temperature of 42 degrees C characterized by increased rectal temperature, respiratory rate, and inspiratory effort, with significant blood biochemical changes indicating metabolic acidosis, ending in death and hyperacute rigor mortis; (3) intraperitoneal pretreatment with dantrolene provided 100% protection from the halothane-triggered fulminant malignant hyperthermia episode; (4) significantly increased sensitivity (decreased effective concentration causing 50% of the maximal response) of R163C heterozygous and homozygous myotubes to caffeine, 4-chloro-m-cresol, and K-induced depolarization; (5) R163C heterozygous and homozygous myotubes have a significantly increased resting intracellular Ca concentration compared with wild type; (6) R163C heterozygous sarcoplasmic reticulum membranes have a twofold higher affinity (Kd = 35.4 nm) for [H]ryanodine binding compared with wild type (Kd = 80.1 nm) and a diminished inhibitory regulation by Mg.


CONCLUSIONS
Heterozygous R163C mice represent a valid model for studying the mechanisms that cause the human malignant hyperthermia syndrome.
Yang
Tianzhong
T
Department of Anesthesia, Perioperative and Pain Medicine, Brigham & Women's Hospital, Boston, Massachusetts 02115, USA.
Riehl
Joyce
J
Esteve
Eric
E
Matthaei
Klaus I
KI
Goth
Samuel
S
Allen
Paul D
PD
Pessah
Isaac N
IN
Lopez
José R
JR
D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D001784:Blood Gas Analysis; D001831:Body Temperature / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D004247:DNA / Q000235:genetics; D015246:Deoxyribonuclease EcoRI / Q000235:genetics; D003952:Diagnostic Imaging; D004195:Disease Models, Animal; D005091:Exons / Q000235:genetics; D006221:Halothane / Q000494:pharmacology; D006801:Humans; D008305:Malignant Hyperthermia / Q000235:genetics* / Q000503:physiopathology; D051379:Mice; D018345:Mice, Knockout; D008839:Microelectrodes; D018485:Muscle Fibers, Skeletal / Q000648:ultrastructure; D009154:Mutation / Q000502:physiology*; D009412:Nerve Fibers / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics*
D018685:Anesthetics, Inhalation; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D012313:RNA; D004247:DNA; D015246:Deoxyribonuclease EcoRI; D002118:Calcium; D006221:Halothane