RESUMO
AIMS: The aims were to develop a method for real-time detection of histamine release and to test whether incubation with aldosterone induces histamine release from isolated, perfused mice mesenteric arteries. METHODS: Fura-2-loaded HEK-293 cells transfected with the histamine H1 receptor was used as a sensitive biosensor assay for histamine release from isolated mouse mesenteric arteries. Activation of the H1 receptor by histamine was measured as an increased number of intracellular Ca2+ transient peaks using fluorescence imaging. RESULTS: The developed biosensor was sensitive to histamine in physiological relevant concentrations and responded to substances released by the artery preparation. Aldosterone treatment of mesenteric arteries from wild-type mice for 50 min resulted in an increased number of intracellular Ca2+ transient peaks in the biosensor cells, which was significantly inhibited by the histamine H1 blocker pyrilamine. Mesenteric arteries from mast cell-deficient SASH mice induced similar pyrilamine-sensitive Ca2+ transient response in the biosensor cells. Mesenteric arteries from wild-type and SASH mice expressed histamine decarboxylase mRNA, indicating that mast cells are not the only source of histamine release. CONCLUSION: The developed biosensor assay can measure release of substances from vascular preparations. Histamine is released from the vessel preparation in response to aldosterone treatment independently of mast cells. The assay enables us to study a new signaling mechanism for vascular responses induced by aldosterone.