Effect of acute anaesthesia on synthesis of contractile and non-contractile proteins of heart muscle and mixed proteins of types I and II fibre rich skeletal muscles of rat

Study objective - The aim of the study was to determine whether the deleterious effects of anaesthesia on cardiac muscle function were due to disturbance of protein synthesis. Comparative investigations were made on anaerobic and aerobic skeletal muscles, and plasma insulin and growth hormone levels were also measured to see if these were mediating factors.Design - Rats were subjected to acute methoxy-fluorane anaesthesia for 10 min. At the end of the study they were killed and plasma growth hormone and insulin were measured. Rates of cardiac and skeletal muscle protein synthesis were also determined with a flooding dose of L[4-³H]phenylalanine.Experimental material - Muscle samples were obtained from male Sprague-Dawley rats, weight 191-222 g.Measurements and main results - Anaesthesia reduced the fractional rate of myocardial mixed protein synthesis and synthesis relative to RNA (p<0.05). The anaesthesia induced decrease in the synthesis rates of cardiac contractile proteins (p<0.05) was greater than the decrease in the non-contractile protein fractions (p>0.05). Soleus (aerobic, Type I) and plantaris (anaerobic, Type II) muscle rates of protein synthesis were unaltered in response to anaesthesia (p>0.05). Plasma insulin concentrations increased in response to acute anaesthesia (p<0.05), but the insulin effect was depressed by the flooding dose of phenylalanine (p<0.05). Plasma growth hormone levels were not altered in response to anaesthesia (p>0.05). Thus, the changes in cardiac protein synthesis could not be ascribed to these hormones.Conclusions - Synthesis of cardiac contractile proteins is selectively sensitive to the effects of acute anaesthesia even in the presence of high plasma insulin concentrations. The fall in cardiac protein synthesis may be a result of the negative inotropic effects of general anaesthesia.