CLOT RETRACTION AND ENERGY METABOLISM OF PLATELETS . EFFECT AND MECHANISM OF INHIBITORS

1. 1. Clot retraction in a system containing buffered saline, fibrinogen, washed blood platelets and thrombin was inhibited by addition of 6-20 ng antimycin or oligomycin per mg platelet protein. The inhibition was counteracted by glucose. 2. 2. Platelet respiration was inhibited 80-90% by addition of 6-20 ng antimycin or oligomycin per mg platelet protein. 3. 3. Monoiodoacetic acid inhibited retraction almost completely, while 2-deoxy-D-glucose and NaF inhibited it partially. Glycolytic inhibitors and antimycin added in combination completely blocked retraction. 4. 4. Washed platelets labeled with radioactive phosphorus and incubated under different conditions were studied. Addition of thrombin caused a sharp drop in radioactivity in ATP and a minor drop in ADP. 5. 5. Incubation with deoxyglucose caused an accumulation of radioactivity in deoxyglucose 6-phosphate; with monoiodoacetic acid, accumulation in fructose 1,6-diphosphate and secondarily in fructose 6-phosphate; with fluoride, accumulation in 3-phosphoglyceric acid and secondarily in fructose 1,6-diphosphate. 6. 6. Incubation with antimycin in the presence or absence of glycolytic inhibitors caused a shift of radioactivity to inorganic phosphate. 7. 7. Incubation with inhibitors in all cases reduced the radioactivity of ATP and ADP to trace amounts. 8. 8. It was concluded that the effect of inhibitors of respiration and glycolysis on clot retraction was caused by the reduction in ATP production in the presence of these agents. © 1960.