The Effect of Short-Term Intermittent Hypoxia Exposure on Mouse Myocardial Oxidative Stress and Cardiac Function

Abstract

To investigate the effect of short-term intermittent hypoxia (IH) on the structure and function of mouse myocardium. Thirty male C57BL6/J mice were randomly assigned to two groups, a control (Con) group and an IH group exposed to hypoxic treatment at atmospheric pressure. The IH group received 10% oxygen pretreatment for 8 hours per day on 14 consecutive days, while the Con group was exposed to normoxia environment and all the other treatment the group received were identical to those given to the IH group, The body mass of the mice was monitored daily during the treatment. The exercise tolerance and the cardiac function of isolated heart were assessed at the end of IH exposure. Additionally, analysis was conducted regarding myocardial enzymology, histology, and other indicators relevant to oxidative stress, including protein carbonylation and lipid peroxidation. There was no significant difference in the exercise tolerance between the two groups. Nevertheless, IH mice showed enhanced cardiac function during isolated heart perfusion ( P<0.05). As compared to the control group, prominent alterations of myocardial structure were detected by transmission electron microscopy of the IH heart, accompanied by elevated creatine kinase-MB levels ( P<0.05). The levels of myocardial reactive oxygen species, protein carbonylation and lipid peroxidation were all significantly upregulated in the IH group as compared to the control group ( P<0.05). IH exposure induced myocardial oxidative stress damage and myofibrillar structural alteration in mice, but did not impair the exercise tolerance of the mice or the contractile function of the isolated heart.