Triglycerides, not phospholipids, are the source of elevated free fatty acids in muscle from patients susceptible to malignant hyperthermia.

In the absence of halothane challenge, incubates of skeletal whole-muscle homogenates from malignant-hyperthermia-susceptible humans and pigs exhibit greater free fatty acid production than controls, which has been attributed to elevated phospholipase A2 activity. The present study examines lipid profiles of human muscle (vastus lateralis) prior to halothane challenge, relating the lipid profiles to the magnitude of halothane contracture response in muscle from the same biopsy. No differences in cholesterol, phospholipids or free fatty acids were observed among preparations exhibiting low, moderate or strong responses to halothane. Two fatty acids associated with triglycerides (palmitoleic and oleic) were significantly (P less than 0.05) lower in muscle demonstrating a strong response to halothane. These results do not support altered phospholipase A2 activity as a defect in malignant hyperthermia, but rather support an enhanced turnover of triglycerides in biopsied skeletal muscle from MH-susceptible humans.