Turnover of adenosine in plasma of human and dog blood.
To determine half-life and turnover of plasma adenosine, heparinized blood from healthy volunteers was incubated with radiolabeled adenosine in the physiological concentration range of 0.1-1 microM. Plasma levels of adenosine in vitro were 82 +/- 14 nM and were similar to those determined immediately after blood collection with a "stopping solution." Dipyridamole (83 microM) and erythro-9(2-hydroxynon-3yl)-adenine (EHNA) (8 microM) did not measurably alter basal adenosine levels but completely blocked the uptake of added adenosine. Inhibition of ecto-5'-nucleotidase with 100 microM alpha, beta-methyleneadenosine 5'-diphosphate (AOPCP) reduced plasma adenosine to 22 +/- 6 nM. For the determination of adenosine turnover, the decrease in specific radioactivity of added [3H]adenosine was measured using a dipyridamole-containing stopping solution. Without altering basal adenosine levels, the half-life was estimated to be 0.6 s. Similar experiments were carried out with washed erythrocytes or in the presence of AOPCP, yielding half-lives of 0.7 and 0.9 s, respectively. When the initial adenosine concentration was 1 microM, its specific activity decreased by only 11% within 5 s, whereas total plasma adenosine exponentially decreased with a half-life of 1.5 s. Venous plasma concentrations were measured after relief of a 3-min forearm ischemia. Changes in plasma adenosine did not correlate well with changes in blood flow but were augmented in the presence of dipyridamole.(ABSTRACT TRUNCATED AT 250 WORDS)
Möser
G H
GH
Zentrum für Physiologie und Klinische Physiologie, Universität Düsseldorf, Federal Republic of Germany.
Schrader
J
J
Deussen
A
A
D015720:5'-Nucleotidase; D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000241:Adenosine / Q000097:blood*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000097:blood; D043383:Adenosylhomocysteinase; D000818:Animals; D001783:Blood Flow Velocity; D004176:Dipyridamole / Q000494:pharmacology; D004285:Dogs; D005542:Forearm / Q000098:blood supply; D006207:Half-Life; D006801:Humans; D006867:Hydrolases / Q000097:blood; D009708:Nucleotidases / Q000037:antagonists & inhibitors; D014316:Tritium
C523965:alpha,beta-methyleneadenosine 5'-diphosphate; D014316:Tritium; D000249:Adenosine Monophosphate; C010192:9-(2-hydroxy-3-nonyl)adenine; D000244:Adenosine Diphosphate; D004176:Dipyridamole; D006867:Hydrolases; D009708:Nucleotidases; D015720:5'-Nucleotidase; D043383:Adenosylhomocysteinase; D000225:Adenine; D000241:Adenosine