title: Effects of antimycin and 2-deoxyglucose on adenine nucleotides in human platelets. Role of metabolic adenosine triphosphate in primary aggregation, secondary aggregation and shape change of platetets.
abstract: 1. Human platelet-rich plasma prelabelled with [(3)H]adenine was incubated at 37 degrees C with antimycin A and 2-deoxy-d-glucose. Variations in the amounts of ATP, ADP and P(i), and in the radioactivity of ATP, ADP, AMP, IMP, hypoxanthine+inosine and adenine were determined during incubation. Adrenaline- and ADP-induced platelet aggregation and the ADP-induced shape change of the platelets were determined concurrently. 2. 2-Deoxyglucose caused conversion of [(3)H]ATP to [(3)H]hypoxanthine+inosine. The rate of this conversion increased with increasing 2-deoxyglucose concentration and was markedly stimulated by addition of antimycin, which had no effect alone. At maximal ATP-hypoxanthine conversion rates, the IMP radioactivity remained at values tenfold higher than control, whereas [(3)H]ADP and [(3)H]AMP radioactivity gave variations typical for product/substrates in consecutive reactions. The specific radioactivityof ethanol-soluble platelet ATP decreased during incubation to less than one-tenth of its original value. The amounts and radioactivity of ethanol-insoluble ADP did not vary during incubation with the metabolic inhibitors. 3. The rate of ADP- and adrenaline-induced primary aggregation decreased as the amount of radioactive ATP declined, and complete inhibition of aggregation was obtained at a certain ATP concentration (metabolic ATP threshold). This threshold decreased with increasing concentration of inducer ADP. 4. Secondary platelet aggregation (release reaction) had a metabolic ATP threshold markedly higher than that of primary aggregation. 5. Shape change was gradually inhibited as the ATP radioactivity decreased, and had a metabolic ATP threshold distinctly lower than that of primary aggregation, and which decreased with increasing concentration of ADP. 6. A small but distinct fraction of [(3)H]ATP disappeared rapidly during the combined shape change-aggregation process induced by ADP in platelets incubated with metabolic inhibitors, whereas no ATP disappearance occurred during aggregation in their absence.
mesh_terms: D000225:Adenine / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000032:analysis; D000249:Adenosine Monophosphate / Q000032:analysis; D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism*; D000968:Antimycin A / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects*; D003837:Deoxy Sugars / Q000494:pharmacology*; D003847:Deoxyglucose / Q000494:pharmacology*; D006801:Humans; D007042:Hypoxanthines; D066298:In Vitro Techniques; D007292:Inosine Nucleotides / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D010974:Platelet Aggregation / Q000187:drug effects; D014316:Tritium
chemical_list: D003837:Deoxy Sugars; D007042:Hypoxanthines; D007292:Inosine Nucleotides; D010710:Phosphates; D014316:Tritium; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000968:Antimycin A; D000255:Adenosine Triphosphate; D003847:Deoxyglucose; D000225:Adenine