Effects of intermittent hypoxia on action potential and contraction in non-ischemic and ischemic rat papillary muscle

Although it has been reported that intermittent hypoxia had the anti-arrhyt hmia effect, little is known about the effects on the action potential (AP) and contraction of papillary muscle, as well as the mechanism of anti-arrh ythmia. The purpose of present study is to observe the effects of intermitt ent hypoxia on action potential and contraction of papillary muscle in rat left ventricle simultaneously using conventional intracellular microelectro de and contraction recording. The effects of intermittent hypoxia on AP and contraction during ischemic solution perfusion were also investigated. Aft er exposed to intermittent hypoxia (six hours daily) for 42 days (IH42), du ration (APD(20)) of 20%, 50% (APD(50)) and 90% (APD(90)) repolarization of AP prolonged significantly compared with animals in control (Con). Effectiv e refractory period (ERP) in IH42 also prolonged significantly. Perfused wi th mimic ischemic solution, the changes of electric and mechanical activiti es in IH42 and in 28 days exposure to intermittent hypoxia (IH28) were much smaller than that in Con and IH14. The result of the study suggested that intermittent hypoxia prolonged the APD and ERP, offered the resistance agai nst the ischemic damage on myocardium, which may be the electrophysiologica l basis of the and-arrhythmia of intermittent hypoxia. (C) 2000 Elsevier Sc ience Inc. All rights reserved.