Calcium accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of malignant hyperthermia diagnostic patients and pigs.

Calcium accumulation by the sarcoplasmic reticulum in whole muscle homogenate preparations of malignant hyperthermia-susceptible (MH+) and non-susceptible (MH-) humans and pigs was investigated using a calcium electrode at 35 degrees C. Sarcoplasmic reticulum of MH+ humans and pigs showed normal Ca2+ accumulation, with no difference being observed in the rate and the time taken to achieve maximal accumulation. However, the capacity for Ca2+ accumulation by the sarcoplasmic reticulum in MH+ humans and pigs is considerably less stable than normal after prolonged ageing of the whole muscle homogenate preparations in ice. In MH+ patients, the capacity for Ca2+ accumulation by the sarcoplasmic reticulum showed a decline of 62% at 22 h ageing and 70% at 48 h ageing, as compared with a reduction of only 23% in MH- patients. In MH+ pigs, the sarcoplasmic reticulum showed a 96% deterioration in the capacity for Ca2+ accumulation as compared with a loss of only 40% in MH- pigs at 7 h ageing in ice. In both humans and pigs, the decline in Ca2+ accumulation was prevented by incubating the whole muscle homogenate preparations for 2 h at 35 degrees C prior to ageing the preparations. The diminished Ca2+ accumulating capacity of the sarcoplasmic reticulum in whole muscle homogenate preparations of MH-susceptible individuals in our experimental protocol provides a potential diagnostic test for malignant hyperthermia susceptibility.