Up-regulation of histidine decarboxylase expression and histamine content in B16F10 murine melanoma cells.

OBJECTIVE AND DESIGN: This study was conducted to determine if differences in histidine decarboxylase expression and histamine levels exist between B16F10 melanoma cells and non-cancerous Melan-A melanocytes. METHODS: Immunofluorescence and western blot analysis were used to detect and compare histidine decarboxylase protein levels. Enzyme-linked immunoassay was used to detect, measure, and compare histamine levels. RESULTS: Histidine decarboxylase expression was found to be elevated in the B16F10 cells. Western blot analysis demonstrated levels of histidine decarboxylase protein expression more than twofold higher (p < 0.001) in B16F10 than in Melan-A cells. Histamine levels were 280-fold higher (p < 0.001) in B16F10 (229 ± 15 pg/mg protein) than in Melan-A (0.83 ± 0.03 pg/mg protein) cells. CONCLUSION: Results indicate an up-regulated histaminergic system in the B16F10 melanoma cells when compared to non-cancerous melanocytes. This supports the use of B16F10 cells as a model in which to investigate a potential role of the endogenous histaminergic system in regulating malignant cell function.

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.