Mechanism of ischemic preconditioning mediated by protein kinase C activation caused by ischemia-related lipid metabolites.

1. 腺苷在缺血预处理的进化中起着至关重要的作用。在原位大鼠心脏中使用微透析技术，我们评估了外5′-核苷酸酶（负责腺苷产生的关键酶）的活性，并检查了溶血磷脂酰胆碱（LPC）对间质腺苷产生的影响。将微透析探针植入麻醉大鼠心脏左心室心肌，灌注含有5′-单磷酸腺苷（AMP, 100 muM）的Tyrode溶液。在这个系统中，透析液腺苷被认为是由内源性外泌5′-核苷酸酶催化的AMP的去磷酸化产生的，透析液腺苷的水平被证实是体内外泌5′-核苷酸酶活性的一个方便的测量方法。25和50 muM浓度的LPC使透析液腺苷水平显著提高至122.7 * 4.3% （n=4, p< 0）。0.05), 158.6 * 7.2% (n=5, p< 0.05)；O5)为控制值。蛋白激酶C （PKC）抑制剂Chelerythrine （200 muM）完全消除了LPC （50 muM）增加的透析液腺苷（n=5）。这些数据提供了第一个证据，证明LPC确实通过pkc介导的内源性外源性5′-核苷酸酶的激活，在原位大鼠心脏中增加间质腺苷的浓度。因此，我们认为在缺血区域积累的LPC通过增加组织间质腺苷（一种负责缺血预处理的关键化合物）的浓度，在缺血预处理的进化中发挥作用。

1. Adenosine plays a crucial role in the evolution of ischemic preconditioning. With the use of microdialysis teci-miques in in situ rat hearts, we assessed the activity of ecto-5'-nucleotidase (a key enzyme responsible for adenosine production), and examined the effects of lysophosphatidyicholine (LPC) on the production of interstitial adenosine.2. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rat hearts and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP, 100 muM). With this system, the dialysate adenosine was considered to originate from the dephosphorylation of AMP, catalyzed by endogenous ecto-5'-nucleotidase, and the level of dialysate adenosine was verified to be a handy measure of the ecto-5'-nucleotidase activity in VIVO.3. LPC at concentrations of 25 and 50 muM significantly increased the level of dialysate adenosine to 122.7 * 4.3 % (n=4, p<O.05) and 158.6 * 7.2 % (n=5, p<O.O5) of the control value, respectively. Chelerythrine (200 muM), a protein kinase C (PKC) inhibitor, completely abolished the increase of dialysate adenosine afforded by LPC (50 muM) (n=5).4. These data provide the first evidence that LPC does increase the concentration of interstitial adenosine via the PKC-mediated activation of endogenous ecto-5'-nucleotidase, in in situ rat hearts.5. Thus, it is suggested that LPC accumulated in ischemic region plays a role for evolution of ischemic preconditioning via increased interstitial concentration of adenosine, a key compound responsible for ischemic preconditioning.