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

1.腺苷在缺血预适应的演变中起着至关重要的作用。采用微透析技术，在大鼠原位心脏中检测腺苷合成的关键酶--外-5 '-核苷酸酶的活性，并观察溶血磷脂酰胆碱（LPC）对间质腺苷合成的影响.将微透析探针植入麻醉大鼠心脏的左心室心肌中，并用含有腺苷5 '-单磷酸（AMP，100 μ M）的台氏溶液灌注。利用该系统，透析液腺苷被认为是来源于内源性外-5 '-核苷酸酶催化的AMP的去磷酸化，并且透析液腺苷的水平被证实是体外外-5'-核苷酸酶活性的简便量度。浓度为25和50 μ M的LPC显著增加透析液腺苷水平，分别为对照值的122.7 * 4.3%（n=4，p<0.05）和158.6 * 7.2%（n=5，p<0.05）。白屈菜红碱（200 μ M），一种蛋白激酶C（PKC）抑制剂，完全消除了LPC（50 μ M）对透析液腺苷的增加（n=5）.这些数据提供了第一个证据，即LPC确实通过PKC介导的内源性外-5 '-核苷酸酶的激活增加大鼠原位心脏中间质腺苷的浓度。因此，这表明LPC积累在缺血区域发挥作用的缺血预适应的演变，通过增加间质浓度的腺苷，一个关键的化合物负责缺血预适应。

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.