Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Antecedent exposure of the heart to a brief ischemic period can confer resistance to a future ischemic episode of longer duration via a mechanism termed ischemic preconditioning (IPC). One putative mediator of IPC is protein kinase C (PKC), an enzyme consisting of at least 12 isoforms. This study assessed the subcellular localization of PKC by immunohistochemistry on cryosections from control, ischemic and IPC rabbit hearts to identify possible PKC isoforms involved in protection or injury. In control hearts, 60-80% of myocyte nuclei exhibited staining for PKC-delta. However, nuclear staining for PKC-delta decreased to < 5% in hearts exposed to 30 min of global ischemia. In contrast, PKC-delta staining was present in 30-60% of nuclei after 30 min of global ischemia in hearts preconditioned by a single 5-min global ischemia, 30-min prior to the test ischemia. PKC-mu exhibited a similar staining pattern. Control hearts also displayed diffuse PKC-zeta staining localized mainly in the cytosol. Hearts exposed to 30-min of global ischemia exhibited prominent PKC-zeta staining of the sarcomeres and also developed a significant ischemic contracture. In contrast, PKC-zeta staining remained localized in the cytosol of IPC hearts and none of these hearts developed an ischemic contracture. Thus, our data suggest that PKC-delta and PKC-mu may mediate the protective effects of IPC, whereas PKC-zeta may play a role in ischemia-induced contractile dysfunction.

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Presentation Number SAlukas0723
Keywords: protein kinase C, ischemia, preconditioning, contractility, rabbit