Enhancement by histamine of the contractile effects of leukotriene D4 on extralobar pulmonary arteries isolated from the guinea pig.

A 5 min pretreatment of the proximal half of the main pulmonary artery (PM) with a concentration of histamine that produced a small degree of contraction (about 8% of maximum) resulted in a large increase in the contractile responses produced by cumulatively increasing concentrations of leukotriene D4 (LTD4). LTD4-induced responses in the distal half of the main artery and the right and left main arterial branches were not markedly altered by concentrations of histamine that produced a magnitude of contraction similar to that produced in the PM segment. The data demonstrate that the potentiative interaction between histamine and LTD4 is not dependent on the contractile event per se.