The relative responsiveness to inhaled leukotriene E₄, methacholine and histamine in normal and asthmatic subjects

The relative bronchoconstricting potencies of leukotriene E₄ (LTE₄), methacholine and histamine have been compared in asthmatic and normal subjects. LTE₄ responsiveness in asthmatic subjects, as measured by the dose which produced a 35% fall in specific airways conductance (PD₃₅), ranged from 0.06-24.4 nmol (geom mean 4.1 nmol, n = 20). This was significantly less than the PD₃₅ in normal subjects (range 39.0-370 nmol, geom mean 105 nmol, n = 6; p < 0.001). There was a correlation between LTE₄ and methacholine responsiveness (r = 0.84, p < 0.001) and between LTE₄ and histamine responsiveness (r = 0.79, p < 0.001). LTE₄ was 73 times more potent than methacholine and 112 times more potent than histamine in asthmatic subjects. LTE₄ was 20 times more potent than methacholine and 58 times more potent than histamine in normal subjects. LTE₄ is a potent bronchoconstrictor agent, and LTE₄ responsiveness correlates with both histamine and mechacholine responsiveness.