Inhibition of Thrombocytopenia and 5‐Hydroxytryptamine Release in Anaphylactic Shock by Heparin

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Abstract
After anaphylactic shock increased amounts of 5‐HT in plasma, and lung tissues, a decrease in the circulating number of platelets and increase in the urinary excretion of 5‐hydroxyindole acetic acid (5‐HIAA) were found but no alteration in the amounts of 5‐HT in the intestines. Pretreatment of the animals with heparin prevented these effects and also the release of 5‐HT from cells in sensitized blood after addition of a specific antigen to citrate blood in vitro. Heparin also inhibits the ability of platelets to adsorb 5‐HT in vitro. Dialysis experiments, coagulation time measurements and intravenous injections of 5‐HT on heparin treated animals indicate that heparin has no ability to bind 5‐HT in blood. It is suggested that heparin, being a strongly acid polyelectrolyte, acts on the platelets and their ability to absorb and release 5‐HT and prevents the onset of a transient intravascular coagulation during anaphylaxis.