RESUMO
The resources of released histamine from activated mast cells, as initial effectors of allergic disease, include not only endogenous prepackaged histamine and newly synthesized histamine, but also histamine that is obtained through the de novo reuptake pathway. To investigate the de novo histamine production pathway, a mast cell line, RBL-2H3 Sc98 in which endogenous histamine production is lacking and only the de novo histamine release pathway via transporters is maintained, was used to dissect histamine reuptake in the present study. Histamine content measurements indicated that RBL-2H3 Sc98 cells took up extracellular histamine for storage in granules and subsequent release after stimulation by an antigen. Profiling and inhibition analysis of possible transporters suggested that the plasma membrane monoamine transporter and organic cation transporter 1 may be candidate transporters for histamine uptake from extracellular spaces, and that vesicular monoamine transporter 2 was responsible for intracellular vesicle uptake. These results may provide the foundation to understand the contribution of exogenous histamine to outward histamine release that is mediated by mechanisms other than conventional exocytosis.