Fig. 4. Effect of 4-chloro- m -cresol (4CmC) on dialysate lactate and lactate/pyruvate ratios in malignant hyperthermia–susceptible (MHS) and normal swine. Microdialysis catheters were implanted percutaneously into adductor muscles of the right and left inner thigh of MHS (n = 9) and normal (n = 9) swine. After an initial in situ equilibration period, microdialysis catheters were perfused with normal saline with or without different 4CmC concentrations. Data are expressed as mean ± SEM. Values refer to the first dialysate fraction according to the Materials and Methods section. Measured lactate and lactate/pyruvate ratios in the absence of 4CmC (saline controls) are plotted against X = 0.01 mm to allow logarithmic display of the entire dose–response curves. Formulas used to illustrate the fitted curve in A for the MHS and normal groups were Y = X2.09/(0.38 * X2.09+ 0.15) + 1.26 and Y = X2.091/(3.78 * X2.091+ 4.205) + 0.871, respectively, and formulas used in B for the MHS and normal groups were Y = X1.65/(0.02 * X1.65+ 0.01) + 22.43 and Y = X1.65/(0.146 * X1.65+ 0.002) + 17.86, respectively. * Values are significantly higher than corresponding values in normal swine. # Significantly higher than saline data point in MHS group.