Loss of ectonucleotidases from the coronary vascular bed after ischemia-reperfusion in isolated rat heart

Kaoru Takahashi-Sato,Junko Kimura,Masa-Aki Ito,Isao Matsuoka,Masahiro Murakawa

doi:10.1186/1471-2261-13-53

Abstract

BackgroundEctonucleotidase plays an important role in the regulation of cardiac function by controlling extracellular levels of adenine nucleotides and adenosine. To determine the influence of ischemia-reperfusion injury on ectonucleotidase activity in coronary vascular bed, we compared the metabolic profile of adenine nucleotides during the coronary circulation in pre- and post-ischemic heart.MethodsLangendorff-perfused rat hearts were used to assess the intracoronary metabolism of adenine nucleotides. The effects of ischemia on the adenine nucleotide metabolism were examined after 30 min of ischemia and 30 min of reperfusion. Adenine nucleotide metabolites were measured by high performance liquid chromatography.ResultsATP, ADP and AMP were rapidly metabolized to adenosine and inosine during the coronary circulation. After ischemia, ectonucleotidase activity of the coronary vascular bed was significantly decreased. In addition, the perfusate from the ischemic heart contained a considerable amount of enzymes degrading ATP, AMP and adenosine. Immunoblot analysis revealed that the perfusate from the ischemic heart dominantly contained ectonucleoside triphosphate diphosphohydrolase 1, and, to a lesser extent, ecto-5’-nucleotidase. The leakage of nucleotide metabolizing enzymes from the coronary vascular bed by ischemia-reperfusion was more remarkable in aged rats, in which post-ischemic cardiac dysfunction was more serious.ConclusionEctonucleotidases were liberated from the coronary vascular bed by ischemia-reperfusion, resulting in an overall decrease in ectonucleotidase activity in the post-ischemic coronary vascular bed. These results suggest that decreased ectonucleotidase activity by ischemia may exacerbate subsequent reperfusion injury, and that levels of circulating ectonucleotidase may reflect the severity of ischemic vascular injury.

Highlights

Ectonucleotidase plays an important role in the regulation of cardiac function by controlling extracellular levels of adenine nucleotides and adenosine
Effects of adenine nucleotides and Ado on cardiac function We examined the effects of the administration of adenine nucleotides and Ado into the coronary circulation on the cardiac function using the Langendorff perfusion of isolated rat hearts
When ATP and ADP were injected into the perfusate, they were almost completely metabolized to AMP and Ado during a single pass (5–10 sec) through the coronary circulation (Figure 1A, B)

Summary

Introduction

Ectonucleotidase plays an important role in the regulation of cardiac function by controlling extracellular levels of adenine nucleotides and adenosine. In the coronary vascular bed, ENTPD1 (CD39) [7,8] and CD73 [9] are thought to be involved in the conversion of ATP to Ado. Recent studies suggested that ectonucleotidase activity is altered under pathophysiological conditions of the heart, such as myocardial ischemia and chronic heart failure [10,11,12,13]. Oxidative stress and inflammatory cytokines inactivate CD39 on the luminal surface of blood vessels, which in turn lead to increased platelet aggregation [12]. These observations suggest that individual enzymes involved in ATP catabolism may be affected differently under various pathophysiological conditions, such as ischemia-reperfusion injury

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