AIMTo study the effects of acute and chronic intermittent hypoxic exposure on the activities of Na+ , K+ -ATPase, Ca2 + , Mg2 + -ATPase of myocardial mitochondria and enzyme complexes of respiratory chain in rats.

METHODSThe activities of Na , K+ -ATPase, Ca2+ , Mg2+ -ATPase of myocardial mitochondria and enzyme complexes of respiratory chain were investigated after chronic intermittent hypoxic exposure (3000 m and 5000 m, 4 h/d, 2 w respectively) and normoxic rats were exposed to hypoxia (8000 m) for 4h.

RESULTS(1) Hypoxia had no effects on the activity of Na+, K+ -ATPase in myocardial mitochondria of rats. (2) Compared with normoxic control rats, the activity of Ca2+, Mg2+ -ATPase in myocardial mitochondria of acute hypoxic rats was reduced significantly. After chronic intermittent hypoxic exposure, its activity was increased significantly compared with that of acute hypoxic rats. (3) Compared with normoxic control rats, the activities of enzyme complex I, II and IV of respiratory chain in acute hypoxic rats were reduced significantly. After chronic intermittent hypoxic exposure, their activities were increased significantly compared with those of acute hypoxic rats. Under the same experimental conditions, hypoxia had no effects on the activity of enzyme complex III.

CONCLUSIONAfter chronic intermittent hypoxic exposure, the activities of Na+, K+ -ATPase, Ca2+, Mg2+ -ATPase of myocardial mitochondria and enzyme complexes of respiratory chain were increased significantly. These suggested that chronic intermittent hypoxic exposure could improve the functions of respiratory chain in myocardial mitochondria and keep the normal energy metabolism.