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Page: << Prev | 1 | 2 | 3 | Next >> This established a link between the mutation, located in a gene that codes for ryanodine receptor proteins, and heat stroke. Ryanodine receptors are channels for calcium to be released into the muscle cell to cause contraction. The mutated calcium channel, the researchers suggested, may allow too much calcium through in response to heat and cause extreme muscle contractions.
"It has long been debated as to whether some cases of heat stroke and exercise-induced muscle breakdown in humans are related to malignant hyperthermia as well," Henry Rosenberg, president of the Malignant Hyperthermia Society of the United States, said in a prepared statement. "This study defines a biochemical pathway that might very well clarify the relationship between anesthesia-induced malignant hyperthermia and heat stroke. This opens new avenues for the study of the not-uncommon problem of heat stroke and exercise-induced muscle breakdown and the risk for malignant hyperthermia."
The team's findings also noted increased calcium ion leakage from the mutated ryanodine receptors during heat stress. The leak contributed to the calcium channels becoming extremely heat sensitive and muscles contracting uncontrollably in response to anesthesia or heat, the researchers said.
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The calcium leak also caused a profound increase in free radical production. Free radicals are molecules that can destroy sensitive cell components and hasten cell death. Free radicals are largely created as a side effect when structures within all human cells, the mitochondria, use oxygen to convert food into energy. Disease processes tend to create more free radicals than the body's naturally occurring antioxidants can handle.
The researchers found that including the antioxidant N-acetylcysteine (NAC) in the mice's water supply, though, greatly decreased their sensitivity to heat stress. NAC is being tested in clinical trials involving patients with cystic fibrosis, where disease creates free radicals that severely damage lung tissue.
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-- Kevin McKeever
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