Abstract
Production of MAPP (1-MAPP and s-MAPP) which can be recovered in CPD-stored platelets after incubation with precursor of MAPP (pre-MAPP) and stimulation in the presence of Ca2+ was not observed in those stimulated by any platelet activators or proteases except thrombin. The use of freeze thawed supernatant of stored platelets, instead of stored platelets, induced MAPP production after incubation with thrombin in the absence of Ca2+, and this reaction was inhibited by antithrombin III.
These results suggest that MAPP are produced from pre-MAPP which have been taken up into platelets in the presence of Ca2+ and modified to the active forms, MAPP, by the action of thrombin in the presence of some platelet factor, and released by activated platelets.
