Energy metabolism in isolated chick ( Gallus domesticus) gastrocnemius and tilapia ( Tilapia mossambica) epaxial muscle at various temperatures in vitro

Muscle respiration experiments on inhibitor dosage (experiment 1), muscle preparation (tendons removed vs. unstretched vs. stretched muscles; chick muscle only; experiment 2) and media temperature (26.5, 32, 37, 42°C; experiment 3) were conducted on chick ( Gallus domesticus) gastrocnemius and tilapia ( Tilapia mossambica) epaxial muscle in vitro. Experiment 1: The dosage of cycloheximide and ouabain required for maximum inhibition of protein synthesis and Na +,K + ATPase, respectively, in chick and tilapia muscle was approximately 6 × 10 −5 M. Experiment 2: Removing the tendons of chick muscle decreased (% inhibition, P = 0.05) cycloheximide-sensitive respiration compared to stretched and unstretched muscles (tendons intact). However, muscle preparation had little influence on ouabain-sensitive respiration. Experiment 3: Cycloheximide-sensitive respiration tended to increase (μ O 2/mg DNA —fhr, P = 0.054) with media temperature in tilapia muscle. Chick muscle was less responsive in this respect. Ouabain-sensitive respiration increased at lower temperature in chick muscle (% inhibition, cubic relationship, P = 0.001) and at higher temperature in tilapia muscle (% inhibition, quadratic relationship, P = 0.0002).