[Inhibitory effect of vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) on bronchoconstriction in guinea pigs].

The present studies were conducted to investigate whether or not VIP and PHI have a bronchodilator effect in vivo. VIP or PHI was administered intravenously in guinea pigs, and dynamic respiratory resistance was measured. Intravenous administration of VIP and PHI reduced dynamic respiratory resistance; however, the effect was significantly less than that of isoprenaline. VIP and PHI inhibited the increase in dynamic respiratory resistance by intravenous administration of histamine in a dose-dependent manner, suggesting that VIP and PHI may be involved in the pathogenesis of airway hyperresponsiveness through inhibiting the effect of mediators on the airway.