The present study was conducted to determine the metabolism of renal interstitial adenosine under resting conditions and during ischemia. By using a microdialysis method with HPLC-fluorometric analysis, renal interstitial concentrations of adenosine, inosine, and hypoxanthine were assessed in pentobarbital-anesthetized dogs. Average basal renal interstitial concentrations of adenosine, inosine,...

The vasodilator adenosine is produced continuously by the normal dog myocardium. However, the relation of adenosine production to increased cardiac metabolism requires clarification. This study tested the hypothesis that increased myocardial Oi demand promotes increased adenosine production to match coronary blood flow (CBF) to metabolic requirements. Increased adenosine production, therefore, ...

The association of a human genetic deficiency of adenosine deaminase activity with combined immunodeficiency prompted a study of the effects of adenosine and of inhibition of adenosine deaminase activity on human lymphocyte transformation and a detailed study of adenosine metabolism throughout phytohemagglutinin-induced blastogenesis. The adenosine deaminase inhibitor, coformycin, at a concentr...

BACKGROUND The inhibitory effect of adenosine on platelet aggregation is abrogated after the addition of adenosine-deaminase. Inosine is a naturally occurring nucleoside degraded from adenosine. OBJECTIVES The mechanisms of antiplatelet action of adenosine and inosine in vitro and in vivo, and their differential biological effects by molecular modeling were investigated. RESULTS Adenosine (...

The elevation of adenosine levels induced by anoxia in isolated rat hepatocytes has been shown to result mainly from an arrest of the recycling of the nucleoside by adenosine kinase [Bontemps, Vincent and Van den Berghe (1993) Biochem. J. 290, 671-677]. To assess the activity of the latter enzyme in intact hepatocytes, incorporation of radioactive adenosine into the cells' adenine nucleotides w...

OBJECTIVE Adenosine dilates human coronary arteries by activating potassium channels in an endothelial cell-independent manner. Cell surface ecto-5'-nucleotidase (CD73) rapidly dephosphorylates extracellular adenosine 5'-monophosphate to adenosine. We tested the hypothesis that coronary vasodilation to adenine nucleotides is mediated by an endothelial CD73-dependent, extracellular production of...

We studied the effect of adenosine on Na+/Ca2+ exchange activity in ewe heart ventricular sarcolemmal vesicles. Adenosine was found to stimulate Na+/Ca2+ exchange activity in a dose-dependent manner from 0.1 nM to 10 microM, with maximal stimulation (40%) at 0.1 microM adenosine. The Vmax of Na+/Ca2+ exchange was increased, but the Km for Ca2+ was not altered. The effect of adenosine was specif...

BACKGROUND Adenosine is a nucleoside, in which an adenine molecule is attached to a ribofuranose sugar moiety. It can be released into the microenvironment by metabolically active cells, and then fulfills a multitude of functions in regulation of cell proliferation, by activating four subtypes of G protein-coupled adenosine receptors. OBJECTIVE In this study, we investigated the effect of ade...

Adenosine has a negative dromotropic effect and modulates hypoxia-induced atrioventricular (AV) conduction delay. To further characterize the negative dromotropic effect of adenosine in the guinea pig heart, we determined the site of adenosine-induced AV conduction block; the effect of uptake and deamination of adenosine on its concentration-negative dromotropic effect, and the adenosine recept...

In the brain, extracellular adenosine increases as a result of neuronal activity. The mechanisms by which this occurs are only incompletely understood. Here we investigate the hypothesis that the Na(+) influxes associated with neuronal signalling activate the Na(+)-K(+) ATPase which, by consuming ATP, generates intracellular adenosine that is then released via transporters. By measuring adenosi...