Effect of brief hypoxia on reperfusion arrhythmias and release of Ca2+ by rat heart homogenate blocked by ryanodine.
OBJECTIVE
We previously reported that a brief period of hypoxic perfusion (BHP) prior to ischemia in rat hearts improved functional recovery upon reperfusion with reduced Ca2+ overload. The present study was designed to determine whether the effect of BHP would be associated with a reduction in reperfusion arrhythmias and a preservation of function of the sarcoplasmic reticulum (SR).


METHODS
Hearts were subjected to 40 min of global ischemia and 30 min of reperfusion after a 20 min period of oxygenated perfusion (oxygenated group: OG), or a 10 min period of oxygenation and 10 min of hypoxic perfusion (hypoxic group: HG). We evaluated the release of Ca2+ by SR blocked by ryanodine, the recovery of left ventricular function, and the reperfusion induced ventricular tachycardia/fibrillation (VT/VF).


RESULTS
Functional recovery improved and the incidence and duration of reperfusion VT/VF were reduced in HG. In HG the uptake of Ca2+ in SR decreased during ischemia, but this decrease was less than that in OG. However, recovery of Ca2+ uptake after reperfusion did not differ between groups. The release of Ca2+ by SR blocked by ryanodine was inhibited in HG throughout the ischemia-reperfusion sequence.


CONCLUSIONS
Observations suggest that the benefits of BHP on recovery of function and reperfusion arrhythmias were associated with a decrease in release of Ca2+ by SR blocked by ryanodine.
Tani
M
M
Department of Geriatric Medicine, Keio University School of Medicine, Tokyo, Japan.
Asakura
Y
Y
Hasegawa
H
H
Shinmura
K
K
Ebihara
Y
Y
Nakamura
Y
Y
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012433:Ryanodine / Q000494:pharmacology*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D000889:Anti-Arrhythmia Agents; D012433:Ryanodine; D002118:Calcium