Presence of a non-splenic platelet pool in man

3 asplenic but otherwise healthy men, in whom autologous platelets had been labelled with radioactive sodium chromate, received i.v. infusions of epinephrine in a dose of 0.35 micrograms per kg per min over a period of 20 min. In response to these infusions an increase in the concentration of labelled platelets (average 8% over the basal value) was seen in all 3 subjects. In no case was the maximal increase in the venous haematocrit higher than 1%. Identical experiments were also carried out on 3 intact male volunteers. As compared to the asplenics, the mean maximal increase in platelet-bound radioactivity was considerably higher (41%). It is concluded that a small but significant epinephrine sensitive non-splenic platelet pool is present in humans.