Heparin and the dextran anaphylactoid reaction in rats.

Injections of heparin had no effect on the dextran anaphylactoid reaction in rats but neutralised the inhibitory action both of protamine and of borate. Heparin, protamine, and borate did not modify the histamine or 5-hydroxytryptamine responses in rat paws and so their effects on dextran may be due to modification of the release mechanisms of these two amines from tissue mast cells.