Expression and Immunohistochemical Localization of Heat-Shock Protein-70 in Preconditioned Porcine Myocardium.

Brief periods of ischemia not only cause a long lasting (hours to days) myocardial contractile dysfunction (stunning) but also increase the tolerance for irreversible damage during a subsequent ischemic episode, a phenomenon called ischemic preconditioning.1J Heat-shock proteins, in particular HSP-70, have been postulated in myocardial protection against irreversible damage due to i~chemia .~ It is known that in vivo as well as in vim, metabolic stressors (e.g., ischemia) and heat lead to the rapid synthesis of 70 kD heat-shock protein (HSP-70) family.3.4 However, the cellular distribution and its potential role in ischemic preconditioning have not yet been well established. Brief periods of myocardial ischemia in rabbits also cause a rapid expression of HSP-70, which is detectable at the protein level within 2 h.4 Recently, we have shown that porcine myocardium responds to ischemia and repehsion by inducing a battery of genes.5-7 In this study, we examined the expression pattern and cellular distribution of HSP-70 in a porcine model of myocardial stunning and preconditioning achieved by two cycles of 10 min of ischemia and 30 min of reperfusion followed by additional 90 and 180 min of reperfusion.