The hypersplenic spleen. A contractile reservoir of granulocytes and platelets.

Epinephrine-induced mobilization of noncirculating granulocytes and thrombocytes was evaluated in 13 subjects with marked variation in spleen size and correlated with the sonographically recorded contraction of the spleen. The effects of epinephrine on blood granulocyte and thrombocyte counts correlated highly with splenic contraction but not with spleen size. The findings provide further insight into mechanisms of hypersplenism, suggest that the big spleen of hypersplenism mimics the contractile reservoir function of the spleen of certain animals, and point out that the "marginal" granulocyte pool mobilized by epinephrine is not randomly distributed throughout the body.