Species differences in platelet function

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The calcium ion sensitive photo-protein aequorin was introduced by incubation into washed platelets of human, monkey, dog, rabbit, and rat. The intracellular calcium ion concentration in mediating thrombin-induced platelet activation differed in value among animals but the phases of efflux were almost the same. Two phases of Ca ion efflux in collagen-induced activation of human, monkey, and rat platelets became one phase upon addition of indomethacin. These findings indicated differences in the values and the phase of intracellular calcium ion efflux with each stimulation in animals.Human, rhesus and cynomolgus monkey blood platelet ATP contents were determined using a commercial RIA kit. The results showed the relation human > rhesus > cynomolgys. The concentration of human platelet factor 4 (PF4) showed a value 5.2-fold that of rabbit, and a value 8.1-8.2-fold that of other animals. These findings indicated differences in the storage pool in the platelets.The proteins and glycoproteins of the human and monkey membranes as determined SDS-polyacrylamide gel electrophoresis showed mutually similar patterns, but were clearly different from those of the other animals.Platelet retention by glass beads was higher in rat than human and decreased with aging in contrast with the case in human.In order to measure the cyclo-oxygenase and lipoxygenase activites in rat platelets, it was necessary to increase the arachidonic acid concentration as substrate. The enzyme activites in the rat were found to be much lower than in human.Difference in the ATP release pattern in ADP stimulated platelets of rabbit and dog suggested the existance of differences in the number and localization of platelet dense granules according to electron microscopic observations.These findings show the necessity of further investigation of species differences in platelet functions.