Effects of glycyrrhizin and glycyrrhetinic acid on dexamethasone-induced changes in histamine synthesis of mouse mastocytoma P-815 cells and in histamine release from rat peritoneal mast cells

The effects of glycyrrhizin and its aglycone, glycyrrhetinic acid, on dexamethasone-induced changes in the histamine synthesis of mastocytoma P-815 cells and in the histamine release from antigen-stimulated rat peritoneal mast cells were investigated. Glycyrrhetinic acid but not glycyrrhizin, at concentrations from 20 to 35 microM, almost completely inhibited the dexamethasone-induced increases in both the histamine content and histidine decarboxylase activity of cultured mastocytoma P-815 cells. Glycyrrhetinic acid, however, showed practically no inhibition of [3H]dexamethasone binding to the cytoplasmic receptor. On the other hand, glycyrrhetinic acid but not glycyrrhizin markedly inhibited the release of histamine from antigen-stimulated rat mast cells, and intensified the inhibitory activity induced by dexamethasone. Glycyrrhetinic acid inhibited the antigen-induced release and incorporation of [3H]arachidonic acid in immunized rat mast cells. The administration of glycyrrhizin into rats, in contrast to the in vitro treatment of the cells with glycyrrhizin, markedly inhibited histamine release from antigen-stimulated rat mast cells. These results suggest that glycyrrhetinic acid inhibited dexamethasone-induced changes in the histamine synthesis of mastocytoma P-815 cells, and in the histamine release from rat mast cells. On the other hand, glycyrrhizin may exert its effect after conversion to glycyrrhetinic acid in vivo.