Differential release of histamine and 5-hydroxytryptamine from rat mast cells: the contribution of amine uptake to the apparent pattern of secretion.

Despite the fact that mast cells isolated from rat mesentery and lung tissue contain 5-HT in excess of histamine, the pattern of amine output, in response to compound 48/80, mirrors that in peritoneal mast cells where histamine is in excess of 5-HT, such that this secretagogue induces a greater percentage release of histamine than 5-HT. Mast cells are capable of taking up both these amines, although uptake of 5-HT is in preference to that of histamine. With concentrations of clomipramine and fluoxetine that inhibited 5-HT uptake, the net percentage release of 5-HT increased in a corresponding manner, and the concentration-effect curves in response to compound 48/80 ran in a collinear fashion with that of control histamine output (measured in the absence of the drugs). Both drugs had no effect upon the uptake or secretion of histamine. Thus, observed differences in the apparent pattern of histamine and 5-HT secretion from rat mast cells may be due to selective reuptake of amines rather than a reflection of differential amine release.