Release of non-mast cell histamine from rat aorta

We previously reported that A23187 induces release of histamine from bovine intrapulmonary vein and provided pharmacological evidence against an involvement of mast cells as the source of histamine. This study was conducted to test more definitively the hypothesis that histamine is released from non-mast cell sources in blood vessels. The effects of A23187 on release of histamine were determined using rat aorta which does not contain mast cells. Aortic rings were mounted for recording of isometric tension, and following exposure to A23187 or vehicle, histamine in the bathing media was measured using enzyme immunoassay. A23187 (100 nmol/l - 10 micromol/l) induced concentration-related release of histamine from rings with endothelium. The accumulation of histamine in the bathing media induced by 10 microM A23187 reached plateau at 60 min (6.2 +/- 1.1 pmol/mg) and was markedly and significantly higher than vehicle control (0.4 +/- 0.1 pmol/mg, p < 0.05). Destruction of endothelium significantly inhibited A23187-induced histamine release (5.5 +/- 1.5 pmol/mg with endothelium, 1.1 +/- 0.3 pmol/mg without endothelium, p < 0.05). The results demonstrate that A23187 induces release of histamine from rat aorta which does not contain mast cells and that the release of histamine is largely dependent on the presence of endothelium.