Effect of adenosine deaminase on cardiac interstitial adenosine.

Adenosine deaminase was infused into isolated perfused guinea pig hearts to determine its effect on myocardial adenosine levels. The enzyme was administered during constant coronary flow perfusion at 6.11 +/- 0.

Incorporation of adenosine and its metabolites into brain nucleotides.

Dogs were subjected to cerebrospinal fluid (CSF) convesity-cisternal perfusion with [U-14C]adenosine, [U-14C]inosine, or [U-14C]hypoxanthine to determine the mechanism of incorporation of these purines into brain adenine nucleotides. After craniotomy, brain tissue was frozen in situ, and the adenine nucleotides were separated by chromatography. A portion of the nucleotide fraction from the brain and [U-14C]purine from CSF were hydrolyzed enzymatically to nucleosides and bases and the specific activities (SA) measured.

Adenosine release during early and sustained exercise of canine skeletal muscle.

During contraction of skeletal muscle in the isolated dog hindlimb under constant-flow perfusion, the specific activity of infused [8- 14C]adenosine (nonvasoactive concn) in venous effluents decreased to 7% of the resting level in 1.25 min and was associated with a concomitant decrease in vascular resistance to 39% of the resting value. Since this decrease in specific activity of labeled adenosine could have been due to 1) an enhanced adenosine release by parenchymal tissue, 2) an exercise-induced increase in the number of open capillaries (greater surface area) in the absence of increased adenosine production 3) some degree of tissue hypoxia, or 4) a combination of these factors, experiments with maximally dilated vessels were performed.

Relationship between adenosine concentration and oxygen supply in rat brain.

Since adenosine is present in normal brain tissue and cerebrosipinal fluid and since it dilates the pial vessels, it is possible that adenosine, in addition to H-+, is also a mediator of the metabolic regulation of cerebral blood flow. Evidence supporting this hypothesis was obtained under various experimental conditions characterized by achange in brain oxygen supply. The brain was frozen in situ by means of a small bonerongeur precooled in liquid N2 and the tissue was processed for adenosine determination (nmol/g of tissue).