Effects of dietary poly-unsaturated fatty acids on tracheal histaminergic and cholinergic responsiveness in experimental models of bronchial hypersensitivity and hyperreactivity.

Respiratory histaminergic and cholinergic receptor function was investigated in isolated tracheal spirals of guinea pigs receiving different diets. Comparison was made between saline treated (controls) and Haemophilus influenzae treated animals in non sensitized conditions, the latter being a model for bronchial hyperreactivity, and in sensitized conditions, being a model for allergen induced bronchial hypersensitivity. The different semi-synthetic diets (35 energy% fat), varying in linoleic acid content (5.85, 11.25 and 22.05 en% fat) and one diet with low linoleic acid (3.55 en%) in which linolenic acid was added additionally (5.30 en%), exerted profound effects on tracheal reactivity to histamine. In sensitized animals the maximal induced histamine contraction was significantly diminished in the dietary group receiving 5.85 en% linoleic acid as compared with the other dietary groups (35% decrease in the H. influenzae-treated, 20-30% decrease in saline treated animals). Results in non-sensitized animals were similar, though less pronounced. No effect on food intake or growth of the animals could be demonstrated during the six week experimental periods. The carbachol induced contraction of the tracheal spirals of sensitized animals receiving low linoleic acid was also significantly decreased as compared to the other dietary groups (30% for saline treated and 20-30% for H. influenzae-treated animals). No difference in carbachol responsiveness could be detected between the different dietary groups under non-sensitized conditions. The results are discussed in view of the current concepts for bronchial hyperreactivity, especially in relation to eicosanoid involvement.