Abstract 13315: Differences in Infarct Size and No-Reflow by Sex in Young Adult Rats in an Electronic Cigarette Exposure Study

Abstract

Purpose: We investigated the effects of chronic exposure to electronic cigarettes (e-cig) on myocardial infarct size and the size of the no-reflow zone in a rat model of both sexes. Methods and Results: Sprague Dawley rats (6 weeks old) were randomized to 4 exposure groups: (1) Purified air (n=16 male/16 female); (2) e-cig vapor with 15mg/mL nicotine (n=13 male/15 female); (3) e-cig vapor without nicotine (n=16 male/12 female); and (4) Standard nicotine-containing combustion cigarette smoke (n=16 male/16 female). All rats were exposed to inhalation exposure for 8 weeks, prior to being subjected to 30 minutes of left coronary artery occlusion followed by 3 hours of reperfusion. Two-way analysis of variance (that factors sex and treatment) demonstrated that chronic exposure to e-cig vapor (with or without nicotine) or to standard cigarettes did not alter myocardial infarct or no-reflow size compared to air. However, as shown in the figure, infarct size was significantly smaller (40.7 ± 2.7% vs 54.5 ± 2.6%; p=0.0004) and no-reflow size was smaller (18.1 ± 2.0% vs 26.8 ± 2.2%; p=0.0042) in female rats compared to male rats. Conclusions: Long-term e-cig exposure did not affect the cardiac sensitivity to ischemia/reperfusion injury in young rats. Female rats are more tolerance to ischemia/reperfusion injury than males. This sex difference phenomena was not observed in our previous study [Li et al. J Thromb Thrombolysis. 1995;2(3):221-225.] that examined the tolerance between males and females subjected to 90 mins of left coronary artery occlusion followed by 4 hours of reperfusion in 1-year-old SD rats and found the myocardial infarct size to be similar between the sexes. The different findings between the 2 studies may be due to the age difference (which implies possible hormonal effects in the younger rats) or different coronary artery occlusion and reperfusion times.