Effect of crowding stress on tolerance to ischemia-reperfusion injury in young male and female hypertensive rats: molecular mechanisms.

Sex and social stress may represent risk factors in the etiology of hypertension and heart response to ischemia-reperfusion (I/R) injury. Phosphatidylinositol 3-kinase/protein kinase B (Akt) plays an important role in the processes associated with hypertension and myocardial tolerance to I/R, and may be involved in myocardial stress reaction. The impact of chronic stress on the response to I/R was investigated in the hearts of 7-week-old spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats of both sexes. Stress was induced by reducing living space to 70 cm(2)/100 g body mass of rat for 2 weeks, while the controls were kept at 200 cm(2)/100 g. Langendorff-perfused hearts, subjected to I/R, exhibited higher vulnerability to ventricular tachycardia in crowd-stressed SHR vs. the control rats, and this was more pronounced in the males. Myocardial infarction was not affected by crowding stress in any of the groups. Male and female SHR showed increased activation of cardiac Akt, whereas nitric oxide synthase activity (NOS) with pro-apoptotic signaling decreased in the males but was not altered in the females (vs. WKY rats). NOS was enhanced in the female SHR and WKY groups by comparison with the respective males. Stress only reduced NOS activity in the SHR groups, and without changes in apoptotic markers. In conclusion, we showed that stress in young SHR mainly affects the nonlethal markers for I/R, and has no impact on myocardial infarction and apoptosis, despite reduced NOS activity.