title: Increasing platelet aggregability after venepuncture is platelet, not plasma derived.
abstract: The time course of ADP induced aggregation of human platelets was determined in aliquots of stored platelet rich plasma 3.5, 10, 30 and 100 minutes after venepuncture. The maximal rate of aggregation was found to increase throughout this entire period, even though pH (7.4), CO2 (7 volume per cent) and temperature (35 degrees C) of the samples were kept constant. The mean acceleration (+/- SEM) between 3.5 and 100 minutes was 41.7 +/- 6.9 per cent (n = 67) at an ADP-concentration of 1 mumol/l and 18.3 +/- 6.2 per cent (n = 23) at 2 mumol/l ADP. The effect did not result from changes of any platelet regulatory factors putatively present alone in the plasma. Acceleration of aggregability was only found when the platelets themselves underwent storage, but not when freshly prepared plasma was given to prestored platelets. The change in aggregability was not diminished after inhibition of platelet cyclooxygenase by oral administration of acetylsalicylic acid.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology; D001792:Blood Platelets / Q000502:physiology*; D001815:Bloodletting; D002255:Carbonic Acid / Q000494:pharmacology; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D010949:Plasma / Q000502:physiology*; D010974:Platelet Aggregation / Q000187:drug effects; D013696:Temperature; D013997:Time Factors
chemical_list: D002255:Carbonic Acid; D000244:Adenosine Diphosphate; D001241:Aspirin