Effect of histamine on human bronchial arteries in vitro

Histamine caused a concentration-dependent relaxation at lower concentrations (1 pmol/l-1 mumol/l) and contraction at higher concentrations (0.01-1 mmol/l) of isolated precontracted human bronchial arteries. In the vessels at resting tension only concentration-dependent contraction was evoked by histamine (0.01-1 mmol/l). Both the contractile and relaxant responses were significantly antagonised by mepyramine (1 mumol/l), with an estimated pKB value of 8.4, but not by cimetidine (100 mumol/l). Our results indicate that histamine induces biphasic effects on human bronchial arteries via H1-receptors.