THE RELEASE AND SUBSEQUENT SYNTHESIS OF HISTAMINE IN A TRANSFECTED SUBCLONE OF RAT BASOPHILIC LEUKEMIA-CELLS THAT EXPRESSES HUMAN MUSCARINIC M1 RECEPTORS

Effects of carbachol and antigen (dinitrophenylated bovine serum album in) on histamine release and histidine decarboxylase (HDC, the enzyme synthesizing histamine) activity were studied in 2H3-m1 cells, a subcl one of rat basophilic leukemia cells that expresses human muscarinic m i receptors through transfection with the gene. Carbachol stimulated t he release of histamine and the activity of HDC with 30-50% the intens ity of the maximal effect of the antigen. Pirenzepine, an mi antagonis t, inhibited these carbachol effects in a dose-dependent manner. The e ffect of the combination of carbachol and antigen on histamine release showed no additivity. These results indicate that these effects of ca rbachol are exerted via mi receptors, and they suggest that the action s of carbachol and antigen on histamine release share a common pathway (s), and the release and synthesis of histamine have a positive relati onship like in a feedback system.