Time course of expression and localization of heat shock protein 72 in the ischemic and reperfused rat heart.

While the role of heat shock protein 72 (HSP72) in protection of the ischemic heart has been studied extensively, the expression and localization of HSP72 in the ischemic and reperfused heart remains poorly understood. This study examined the expression and distribution of HSP72 after various periods of ischemia and reperfusion in the non-stress-pretreated rat heart. The distribution of HSP72 in the myocardium was examined immunohistochemically using a specific monoclonal antibody for detection of this protein. The levels of HSP72 mRNA in the myocardium were estimated by the reverse transcriptase polymerase chain reaction (RT-PCR) method. Rats were subjected to either permanent occlusion of the left coronary artery or 30 min of occlusion followed by reperfusion, and they were sacrificed 30 min, 4 h, 24 h and 7 days thereafter. Both permanent ischemia and reperfusion induced expression of HSP72 mRNA in the ischemic myocardium from 30 min to 24 h after the onset of ischemia/reperfusion. The maximum mRNA level, which appeared at 4 h, was much higher in the reperfusion group than in the permanent ischemia group. Myocytes exhibited definite immunoreactivity of HSP72 at 4 h and 24 h in both groups, and microvessels exhibited strong immunoreactivity at 4 h in the reperfusion group. This study revealed the time course of expression and distribution of HSP72 in the ischemic and reperfused hearts in vivo.