We determined the effect of aerosol challenge with leukotriene D4 (LTD4) on specific lung resistance (sRL) and tracheal mucous velocity (TMV) in conscious sheep with (allergic) and without (nonallergic) Ascaris suum hypersensitivity. In allergic sheep LTD4 in concentrations of 50, 100, and 150 μg/ml produced dose-dependent increases in mean sRL by 44 (P = NS), 154 (P<0.05), and 233% (P<0.05), respectively. The increases in sRL produced by 150 μg/ml LTD4 was prevented by FPL 55712, an antagonist of slow-reacting substance of anaphylaxis. In nonallergic sheep 150 μg/ml LTD4 failed to elicit a significant change in sRL. In contrast to the changes in airway mechanics, concentrations of LTD4 as low as 25 μg/ml produced significant decreases in TMV in allergic sheep. The maximum decrease in TMV at this dose occurred 2 h after challenge; with larger doses of LTD4 (100 and 150 μg/ml) the maximum effect was observed 3 h after challenge. Furthermore, 150 μg/ml LTD4 reduced TMV in nonallergic sheep (mean decrease 43%, P<0.05). FPL 55712 only had a minor effect on the LTD4-induced decreases in TMV. We conclude that allergic sheep exhibit greater airway responsiveness to inhaled LTD4 than nonallergic sheep but that this difference is not evident for the concomitant changes in mucociliary transport. This suggests that the allergic state is associated with an increased responsiveness to LTD4 in tissues controlling airway caliber but not in those contributing to mucociliary function.
ASJC Scopus subject areas
- Physiology (medical)