Chronic exposure of mammals to
hypoxia induces a state of
anorexia. We aimed to determine the role played by diet restriction in the alterations of myocardial energy metabolism occurring under chronic
hypoxia in order to detect the specific effects of
hypoxia per se. Adult female rats were exposed to normobaric
hypoxia (FiO2 = 0.10) for three weeks; pair-fed rats, kept under normoxic conditions, received the same amount of food as hypoxic rats. The oxidative capacity of myocardial ventricles and some skeletal muscles was evaluated using permeabilized fibers. Several metabolic
enzyme activities were measured on extracts from myocardium and soleus. Diet restriction increased the activity of
lactate dehydrogenase in both ventricles while it augmented
phosphofructokinase and
pyruvate kinase activities only in the left ventricle and depressed the respiratory rate in the right ventricle only.
Hypoxia per se induced a rise in
hexokinase activity in all studied oxidative muscles and a fall of hydroxy-
acyl CoA-dehydrogenase activity in both myocardial ventricles. The respiratory rate and the
citrate synthase activities were unaffected by
hypoxia. We conclude that chronic
hypoxia per se leads to specific alterations in myocardial metabolism that could favor the use of exogenous
glucose at the expense of
free fatty acids without any change in the oxidative capacity.