Ionic Binding of Histamine in Mast Cell Granules

Abstract

Histamine‐containing granu!es were isolated from rat mast cells by differential centrifugation. The histamine was released on suspension of the granules in a medium containing sodium. By using radioactive sodium (²²Ta) the release of histamine was shown to be due to an exchange with sodium at ionic sites in the granules. The affinity of histamine was calculated to he about 10 times that o sodium. The pH dependence of the release of histamine and the uptake of sodium agrees with an ionic binding to weak acid groups [carboxylic groups] and not to strong acid groups (sulphate groups) as previously stated. Whether these hindins groups belong to the heparin or the protein in the granules remains to be decided.