1 Roles of histamine in the production of vascular endothelial growth factor (VEGF) in the carrageenin-induced granulation tissue in rats were analysed in vitro and in vivo. 2 Incubation of the minced granulation tissue in the presence of histamine (1 and 10 μM) increased the content of VEGF protein in the conditioned medium in a time- and concentration-dependent manner. The levels of VEGF mRNA in the minced granulation tissue were also increased by histamine in a concentration-dependent manner. 3 The increase in the content of VEGF protein in the conditioned medium by histamine (10 μM) was suppressed by the H2 receptor antagonist cimetidine (IC50 0.37 μM), but not by the H1 receptor antagonist pyrilamine maleate, the H3 receptor antagonist thioperamide or the cyclo-oxygenase inhibitor indomethacin. 4 The histamine-induced increase in the content of VEGF protein in the conditioned medium was inhibited by the cyclic AMP antagonist Rp-cAMP (IC50 6.8 μM), and the protein kinase A inhibitor H-89 (IC50 12.5 μM), but not by the protein kinase C inhibitors Ro 31-8425 and calphostin C or the tyrosine kinase inhibitor genistein. 5 Simultaneous injection of cimetidine (400 μg) and indomethacin (100 μg) into the air pouch of rats additively reduced the carrageenin-induced increase in VEGF protein levels and angiogenesis in the granulation tissue as assessed by using carmine dye. 6 These findings indicate that histamine has an activity to induce VEGF production in the granulation tissue via the H2 receptor-cyclic AMP-protein kinase A pathway and augments angiogenesis in the granulation tissue.
- Granulation tissue
- H2 receptor