Lactation protects against myocardial ischemia-reperfusion injury in rats

Some researchers have reported that lactation is effective in reducing cardiovascular disease risk factors. The purpose of this study was to investigate whether lactation may improve intrinsic tolerance against ischemia reperfusion (IR) injury. The rats were randomly divided into two groups (n = 8 in each group). In the lactation (Lact) group, the surgery was performed on postpartum day 21 (at the end of lactation period) and the results were compared with those of virgin female rats (control group). Cardiac IR injury was induced by means of left anterior descending coronary artery occlusion for 30 min followed by reperfusion for 120 min. Infarct size was measured using the staining agent 2,3,5-triphenyltetrazolium chloride. At the end of the experiment, Mean arterial pressure in the control group was significantly lower than that in the Lact group. Myocardial infarct size was significantly reduced in the Lact group (23 +/- 3% vs. 45 +/- 8%, p < 0.05 in the control group). Lactation reduced the extent of myocardial injury induced by ischemia and reperfusion. So, lactation may increase cardiac tolerance to ischemic injury.