Minamino T, Kitakaze M, Komamura K, Node K, Takeda H, Inoue M, Hori M, Kamada T
First Department of Medicine, Osaka University School of Medicine, Suita, Japan.
Arterioscler Thromb Vasc Biol. 1995 Dec;15(12):2298-304. doi: 10.1161/01.atv.15.12.2298.
Both ischemia and hypoxia increase adenosine production in the heart. This study tested whether hypoxia increases adenosine production in the coronary artery via ecto-5'-nucleotidase and the role of protein kinase C in this condition. Canine left circumflex coronary artery was rapidly removed and incubated in 10 mL Krebs-Henseleit solution for 30 minutes. The Krebs-Henseleit solution contained 5'-iodotubercidin and 2'-deoxycoformycin, which inhibit adenosine kinase and adenosine deaminase, respectively. Adenosine production was measured in intact coronary arteries under normoxic conditions (16.2 +/- 1.2 pmol/mg protein). Adenosine production was reduced by 27% after removal of endothelium. Ecto-5'-nucleotidase activity of coronary arteries with and without endothelium was 51 +/- 6 and 41 +/- 4 nmol/mg protein per minute under normoxic conditions. Hypoxia increased adenosine production to 27.0 +/- 2.3 and 20.0 +/- 0.8 pmol/mg protein with and without endothelium. Hypoxia also increased ecto-5'-nucleotidase activity of coronary arteries with and without endothelium (74 +/- 8 and 53 +/- 5 nmol/mg protein per minute; P < .05). Increases in adenosine production under hypoxic conditions were blunted by both an inhibitor of ecto-5'-nucleotidase and inhibitors of protein kinase C. Activation of ecto-5'-nucleotidase was blunted by an inhibitor of protein kinase C. These results indicate that hypoxia increased extracellular adenosine production and activated ecto-5'-nucleotidase via activation of protein kinase C in coronary arterial smooth muscle and endothelial cells. Increased adenosine production in coronary arteries during hypoxia may contribute to coronary vasodilation and cardioprotection against ischemic injury.
缺血和缺氧均会增加心脏中腺苷的生成。本研究检测了缺氧是否通过胞外5'-核苷酸酶增加冠状动脉中腺苷的生成以及蛋白激酶C在这种情况下的作用。迅速取出犬左旋冠状动脉，并在10 mL Krebs-Henseleit溶液中孵育30分钟。Krebs-Henseleit溶液含有5'-碘胸苷和2'-脱氧助间型霉素，它们分别抑制腺苷激酶和腺苷脱氨酶。在常氧条件下（16.2±1.2 pmol/mg蛋白质）测量完整冠状动脉中的腺苷生成量。去除内皮后，腺苷生成量减少了27%。在常氧条件下，有内皮和无内皮的冠状动脉的胞外5'-核苷酸酶活性分别为每分钟51±6和41±4 nmol/mg蛋白质。缺氧使有内皮和无内皮的冠状动脉中的腺苷生成量分别增加至27.0±2.3和20.0±0.8 pmol/mg蛋白质。缺氧还增加了有内皮和无内皮的冠状动脉的胞外5'-核苷酸酶活性（每分钟74±8和53±5 nmol/mg蛋白质；P<0.05）。胞外5'-核苷酸酶抑制剂和蛋白激酶C抑制剂均减弱了缺氧条件下腺苷生成量的增加。蛋白激酶C抑制剂减弱了胞外5'-核苷酸酶的激活。这些结果表明，缺氧通过激活冠状动脉平滑肌和内皮细胞中的蛋白激酶C增加了细胞外腺苷的生成并激活了胞外5'-核苷酸酶。缺氧期间冠状动脉中腺苷生成量的增加可能有助于冠状动脉舒张和对缺血性损伤的心脏保护作用。
