Mitochondrial Traits of Muscle from Stress-Susceptible Pigs

Abstract

The purpose of this investigation was to study the respiratory functions of skeletal muscle mitochondria isolated from 12 pigs of similar breeding that were equally divided as stress susceptible (SS) and stress resistant (SR), depending on their response to halothane (Fluothane®) anesthesia. Skeletal muscle samples were collected by biopsy 2 to 4 weeks before slaughter, immediately post-mortem and 3 hr post-mortem. As the muscle pH decreased from a mean value of 7.08 to 6.39, state 3 and state 4 respiration, respiratory control index and ADP/O ratio were reduced. No mitochondrial respiratory activity was observed below muscle pH 5.90. Statistical analysis was confined to biopsy and immediately post-mortem values because of lack of respiratory activity in all mitochondrial preparations from SS pigs at 3 hr post-mortem. For the remaining two sampling periods, no significant interactions were observed between time of sampling and type of pig for any of the respiratory traits measured. Type of pig did not show a significant relationship between state 3, state 4 or the ADP/O ratio when biopsy values were compared. Therefore, the mitochondrial characteristics studied do not appear to be involved in the etiology of the porcine stress syndrome. When muscle tissue was obtained immediately after death, the stress-susceptible pigs had significantly (P<.01) lower state 4 values, and the state 3 values were approaching significance (P<.07). The respiratory response probably was caused by a significantly (P<.01) lower muscle pH for the stress-susceptible pigs when evaluated immediately post-mortem.