Figure 4. (A) Effect of propofol on the Calcium2+-adenosine triphosphatase (Calcium2+-ATPase) activity of sarcoplasmic reticulum vesicles. The Calcium2+-ATPase activity of malignant hyperthermia (MH)-susceptible (filled circles) and normal (open circles) preparations was measured at 22 degrees Celsius, pH 7.0. (B) Effect of propofol on [45]Calcium2+ uptake by skeletal muscle membrane vesicles. ATP-dependent Calcium2+ uptake by MH-susceptible and normal preparations was measured at 22 degrees Celsius, pH 7.0, in the presence of 100 micro Meter ruthenium red. Control activities in the absence of propofol were 0.28 plus/minus 0.03 micro mol inorganic phosphate *symbol* mg protein1*symbol* min1(A) and 0.59 plus/minus 0.07 micro mol Calcium2+*symbol* mg protein1*symbol* min1(B). All points represent means plus/minus SE of duplicate measurements from three MH-susceptible and three normal preparations.