ADENINE NUCLEOTIDE METABOLISM OF BLOOD PLATELETS .I. ADENOSINE KINASE AND NUCLEOTIDE FORMATION FROM EXOGENOUS ADENOSINE AND AMP

1. 1. The metabolism of [14C10]adenosine and [14C10]AMP added to| platelet-rich plasma, washed platelets in saline and platelet extracts was investigated. 2. 2. The metabolites were extracted with ethanol, identified by radioautography and their radioactivity measured after two-dimensional paper chromatography. 3. 3. Approx. 30 % of the [14C10]adenosine was transported into the platelets and appeared mainly as radioactive ADP and ATP whereas the remainder was converted in plasma via inosine to hypoxanthine and two unidentified compounds. 4. 4. AMP was not transported across the platelet membrane, but first had to be dephosphorylated to adenosine in plasma. 5. 5. Platelet lysates in presence of ATP and Mg2+ (or Mn2+) converted [14C10]-adenosine to radioactive AMP, ADP and ATP. The reaction was optimal at pH 5.6 and it was shown that radioactive AMP was the immediate product, but its radio-activity was converted to ATP and ADP within a few seconds by platelet adenylate kinase. The lysates did not incorporate either [8-14C]adenine in the presence of ribose 1-phosphate or 32Pi into adenine nucleotides, suggesting that the adenosine-AMP conversion was catalyzed by adenosine kinase. 6. 6. Platelet lysates contained adenosine deaminase, 5′-AMP-deaminase as well as purine nucleoside phosphorylase. © 1968.