Plasma cortisol levels in pigs susceptible and resistant to malignant hyperthermia

Plasma cortisol levels were measured in Landrace pigs susceptible to malignant hyperthermia (MH), Landrace pigs resistant to MH and in Largewhite pigs, during growth halothane anaesthesia and after injections of Synachten. From 3 to 6 months of age mean cortisol levels in susceptible Landrace were 193,2 +/- 49,7 nmol/l, in resistant Landrace 220,8 +/- 24,8 nmol/l and in Largewhite 278,8 +/- 13,8 nmol/l. These values were not significantly different. After injection of 1 mg Synachten intravenously, plasma cortisol levels did not increase significantly in susceptible pigs. In resistant landrace pigs and Largewhite pigs the plasma levels after injection were significantly greater than pre-injection levels (P less than 0,05) and significantly different from susceptible Landrace levels. During halothane anaesthesia, cortisol levels rose more in resistant pigs than in susceptible pigs, but differences were no significant. These results suggest that susceptible pigs have a decreased ability to secrete cortisol during stress.