[Effects of hypoxic acclimatization on myocardial sarcoplasmic reticulum ATPase and 45Ca2+ uptake in rats].
OBJECTIVE
To study the effect of acute hypoxia and hypoxic acclimatization on myocardial function of rats.


METHODS
Eighteen male Wistar rats were randomly divided into three groups: normoxic control, acute hypoxia and intermittent hypoxic acclimatization group (n=6). After being exposed to hypoxia (8000 m) for 4 h before and after intermittent hypoxic acclimatization (3000 m and 5000 m, 14 d respectively, 4 h/d), the rats were decapitated and then myocardial sarcoplasmic reticulum (SR) were derived from cardiac muscles. Activities of Na+, K(+)-ATPase, Ca2+, Mg2(+)-ATPase in SR, phosphorylation of phospholamban (PLB) and the ability of 45Ca2+ uptake in SR were observed in all these three groups.


RESULTS
1) Hypoxia had no effects on the activity of Na+, K(+)-ATPase in rats myocardial SR of rats. 2) Compared with normoxic control rats, the activity of Ca2+, Mg2(+)-ATPase in myocardial SR of rats after acute hypoxia was reduced significantly (P<0.01). After intermittent hypoxic acclimatization, its activity increased significantly as compared with that of acute hypoxic rats (P<0.01). 3) The phosphorylation of PLB in acute hypoxic rats was reduced significantly compared with normoxic control rats. After intermittent hypoxic acclimatization, its phosphorylation was increased significantly compared with that of acute hypoxic rats. It suggests that hypoxic acclimatization could alleviate the inhibition of calcium pump. 4) The ability of 45Ca2+ uptake of SR in acute hypoxic rats was decreased significantly. After hypoxic acclimatization, its ability was strengthened significantly.


CONCLUSIONS
These results suggest that the increased function of myocardial SR calcium pump, the strengthened phosphorylation of PLB to alleviate the inhibition of calcium pump and the increased function of Ca2+ transport in SR are the mechanisms of hypoxic acclimatization protecting cardiac functions from injury induced by severe hypoxia.
Long
Chao-liang
CL
Institute of Toxicology and Pharmacology, Academy of Military Medical Sciences, Beijing, China.
Zhang
Yan-fang
YF
Yin
Zhao-yun
ZY
Wang
Hai
H
D000064:Acclimatization; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000531:Altitude; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D027682:Cation Transport Proteins; D004195:Disease Models, Animal; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D000099211:Phospholamban
D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; D012964:Sodium; D000099211:Phospholamban; C022761:potassium transporting ATPase