title: Activation of protein kinase C increases adenosine production in the hypoxic canine coronary artery through the extracellular pathway.
abstract: 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.
mesh_terms: D015720:5'-Nucleotidase / Q000378:metabolism; D000241:Adenosine / Q000096:biosynthesis*; D058892:Adenosine Deaminase Inhibitors; D000248:Adenosine Kinase / Q000037:antagonists & inhibitors; D000818:Animals; D001158:Arteries / Q000378:metabolism; D003331:Coronary Vessels / Q000378:metabolism*; D004285:Dogs; D004789:Enzyme Activation; D000860:Hypoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D015649:Pentostatin / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D014372:Tubercidin / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D058892:Adenosine Deaminase Inhibitors; C034214:5-iodotubercidin; D015649:Pentostatin; D000248:Adenosine Kinase; D011493:Protein Kinase C; D015720:5'-Nucleotidase; D000241:Adenosine; D014372:Tubercidin