The influence of exercise and diet on myoglobin and metmyoglobin reductase in the rat.

: This study was designed to evaluate the influence of exercise and diet on selected aspects of heme protein metabolism in the rat. Two levels of treadmill exercise and three levels of dietary restriction were imposed on growing male rats over a 12-week experimental period. Neither training nor diet had any effect on erythrocyte NADH-MetHB reductase. The group undergoing the highest level of treadmill exercise had a significantly lower HB concentration. The activity of NADH-MetMB reductase was increased in the group undergoing the highest level of training and decreased in the groups whose diet was restricted by 25% and 35%. These changes were seen only in the soleus muscle. Other muscles, including the heart, psoas, and quadriceps were unaffected by either exercise of diet. Both levels of exercise were effective in increasing muscle MB concentration, but only in the quadriceps and soleus muscles. These data illustrate the adaptive nature of muscle MB and NADH-MetMB reductase. They also illustrate the different adaptive patterns of these two components of muscle.