Fig. 5. 4-Chloro -m -cresol (4-C  m C) concentration–response stimulation of B lymphocytes. Concentration–response curves to 4-C  m C and regression analysis of mean values (± SD; where n = 6 for each cell line used) of ⁴⁵Ca²⁺released induced by the indicated concentrations of 4-C  m C.  R =0.94 (  P =0.0064) for malignant hyperthermia–susceptible (MHS) family 1 (  fig. 1, IV:2 and V:13);  R =0.94 (  P =0.0062) for MHS family 2 (  fig. 3, II:4), and  R =0.97 (  P =0.0097) for malignant hyperthermia–negative (MHN) individuals from both families (  fig. 1, V:10 and V:15, and  fig. 3, III:4). The confidence interval was set at 95%. Half-maximal release of ⁴⁵Ca²⁺induced by 4-C  m C occurred at 370 μm for lymphocytes from both MHS individuals and at 610 μm for MHN lymphocytes. Observed counts-per-minute values in all experiments were normalized to the intensities obtained with 800 nm thapsigargin considered to be 100%, and the amount of ⁴⁵Ca²⁺released by the different concentrations of 4-C  m C was calculated as a percentage relative to the amount released by 800 nm thapsigargin.