Effects of Remote Ischemic Preconditioning on the Expressions of NOS and Akt in the Rat Myocardium

Jo, Ji Yon; Seo, Youn Kyoung; Jeon, Su Kyoung; Paik, Doo Jin

Abstract

Remote ischemic preconditioning (IP), brief tolerating cycles of ischemia and reperfusion in remote non-vital organs, can reduce ischemic injury of the heart. IP induces cardiac protection by down-regulating iNOS or up-regulating eNOS. In addition, Akt has been known to protect myocardium against ischemia-reperfusion injury. This study was undertaken to observe the expression of iNOS, eNOS, Akt and phospho-Akt (p-Akt) in the rat myocardium after IP. Thirty-five weeks-old male Sprague-Dawley rats were divided into control and IP groups. The IP group was further subdivided into 3 groups based on the number of cycles of IP. For IP, left commom iliac artery was occluded 3, 6 and 10 cycles for 5 min of ischemia alternating with 5 min of reperfusion. The rat were sacrificed at 0, 3, 6, 24 and 72 hours of IP and the heart was removed. The expression of iNOS, eNOS, Akt and p-Akt in the rat myocardium was examined by immunohistochemical staining and Western blot analysis. The expression of iNOS was increased by IP and was higher in 10IP groups than 3IP and 6IP group. The expression of eNOS was increased or decreased by IP and was showed no difference with increasing episode of IP. The expression of Akt was decreased by IP at 24 and 72 hours after reperfusion, and showed no differences with increasing episode of IP. The expression of p-Akt was increased by IP and showed no difference with increasing episode of IP. These results suggest that hind limb ischemic preconditioning provides cardiac protection through up-regulation of eNOS and phosphorylation of Akt, however excessive episodes of remote preconditioning may induce the myocardial ischemic injury through overexpression of iNOS.