Tosaki A, Maulik N, Engelman D T, Engelman R M, Das D K
University of Connecticut Health Center, School of Medicine, Farmington 06032-1110, USA.
J Cardiovasc Pharmacol. 1996 Nov;28(5):723-31. doi: 10.1097/00005344-199611000-00016.
Protein kinase C (PKC) has been implicated in the preconditioning-induced cardiac protection in ischemic/reperfused myocardium. We studied the effect of PKC inhibition with calphostin C (25, 50, 100, 200, 400, and 800 nM), a potent and specific inhibitor of PKC, in isolated working nonpreconditioned and preconditioned ischemic/reperfused hearts. In the nonpreconditioned groups, all hearts underwent 30 min of normothermic global ischemia followed by 30 min of reperfusion. In the preconditioned groups, hearts were subjected to four cycles of ischemic preconditioning by using 5 min of ischemia followed by 10 min reperfusion, before the induction of 30 min ischemia and reperfusion. At low concentrations of calphostin C (25, 50, and 100 nM), the PKC inhibitor had no effect on the incidence or arrhythmias or postischemic cardiac function in the nonpreconditioned ischemic/reperfused groups. With 200 and 400 nM of calphostin C, a significant increase in postischemic function and a reduction in the incidence of arrhythmias were observed in the nonpreconditioned ischemic/reperfused groups. Increasing the concentration of calphostin C to 800 NM, the recovery of postischemic cardiac function was similar to that of the drug-free control group. In preconditioned hearts, lower concentrations (< 100 nM) of calphostin C did not change the response of the myocardium to ischemia and reperfusion in comparison to the preconditioned drug-free myocardium. Two hundred and 400 nM of the PKC inhibitor further reduced the incidence of ventricular fibrillation (VF) from the preconditioned drug-free value of 50% to 0 (p < 0.05) and 0 (p < 0.05), respectively, indicating that the combination of the two, preconditioning and calphostin C, affords significant additional protection. Increasing the concentration of calphostin C to 800 nM blocked the cardioprotective effect of preconditioning (100% incidence of VF). The recovery of cardiac function was similarly improved at calphostin C doses of 200 and 400 nM and was reduced at 800 nM (p < 0.05). With 200 and 400 nM of calphostin C, both cytosolic and particulate PKC activity were reduced by approximately 40 and 60%, respectively, in both preconditioned and preconditioned/ischemic/reperfused hearts. The highest concentration of calphostin C (800 nM) resulted in almost a complete inhibition of cytosolic (100%) and particulate (85%) PKC activity correlated with the abolition of preconditioning-induced cardiac protection. In conclusion, calphostin C protects the ischemic myocardium obtained from intact animals, provides significant additional protection to preconditioning at moderate doses, and blocks the protective effect of preconditioning at high concentrations. The dual effects of calphostin C appear to be strictly dose and "enzyme inhibition" related.
蛋白激酶C（PKC）已被证明与缺血/再灌注心肌的预处理诱导的心脏保护作用有关。我们研究了PKC特异性强效抑制剂钙泊三醇C（25、50、100、200、400和800 nM）对离体非预处理和预处理的缺血/再灌注工作心脏的影响。在非预处理组中，所有心脏均经历30分钟的常温全心缺血，随后再灌注30分钟。在预处理组中，心脏在诱导30分钟缺血和再灌注之前，先进行四个缺血预处理周期，即5分钟缺血后再灌注10分钟。在低浓度钙泊三醇C（25、50和100 nM）时，PKC抑制剂对非预处理的缺血/再灌注组的心律失常发生率或缺血后心脏功能没有影响。使用200和400 nM钙泊三醇C时，在非预处理的缺血/再灌注组中观察到缺血后功能显著改善，心律失常发生率降低。将钙泊三醇C浓度增加到800 nM时，缺血后心脏功能的恢复与无药物对照组相似。在预处理的心脏中，与未用药物预处理的心肌相比，较低浓度（<100 nM）的钙泊三醇C不会改变心肌对缺血和再灌注的反应。200和400 nM的PKC抑制剂分别将预处理未用药物组50%的室颤（VF）发生率进一步降低至0（p<0.05）和0（p<0.05），表明预处理和钙泊三醇C两者联合提供了显著的额外保护。将钙泊三醇C浓度增加到800 nM时，阻断了预处理的心脏保护作用（VF发生率为100%）。在200和400 nM钙泊三醇C剂量下，心脏功能的恢复同样得到改善，而在800 nM时则降低（p<0.05）。使用200和400 nM钙泊三醇C时，在预处理和预处理/缺血/再灌注的心脏中，胞质和颗粒状PKC活性分别降低了约40%和60%。钙泊三醇C的最高浓度（800 nM）导致胞质（100%）和颗粒状（85%）PKC活性几乎完全抑制，这与预处理诱导的心脏保护作用的消除相关。总之，钙泊三醇C可保护来自完整动物的缺血心肌，在中等剂量时为预处理提供显著的额外保护，而在高浓度时阻断预处理的保护作用。钙泊三醇C的双重作用似乎与严格的剂量和“酶抑制”有关。
