Protein kinase C mediates Ca2+-induced cardioadaptation to ischemia-reperfusion injury

Although protein kinase C (PKC)-mediated cardioadaptation to ischemia-reperfusion (IR) is accompanied by increased intracellular Ca2+ concentration, it is unknown whether a preischemia sarcoplasmic reticulum (SR) Ca2+ release affects PKC-mediated post-IR functional protection. To study this, crystalloid-perfused (Langendorff) Sprague-Dawley rat hearts were used to assess the effects of a ryanodine (Ry)-induced preischemia Ca2+ load (Ry, 5 nM/2 min, retrograde coronary) 10 min before global IR (20 min). Ry was administered with and without each of two different PRC inhibitors (20 mu M chelery-thrine and 150 nM bisindolylmaleimide I-HCl). Ry improved myocardial functional recovery (developed pressure, end-diastolic pressure, coronary flow, and creatine kinase activity), which was eliminated after PKC inhibition. Immunohistochemical staining for PKC isoforms demonstrated that Ry induces specific PKC translocation of alpha-, delta-, and zeta-isoforms, We conclude that 1) a preischemia Ca2+ load from the SR results in post-IR myocardial functional protection, 2) Ca2+-induced functional protection is PKC regulated via the translocation of specific isoforms, and 3) Ca2+-induced cardioadaptation to IR injury may have important therapeutic implications prior to planned ischemic events such as cardiac allograft preservation and cardiac bypass surgery.