GUINEA-PIG LUNG STRIP - STUDY OF THE MEDIATORS OF THE SCHULTZ-DALE REACTION

A new in vitro preparation, the isolated lung strip of the guinea-pig, is described for investigating the Schultz-Dale reaction and the effect of drugs on the smooth muscles of the lung. Histamine caused a contraction of the preparation. This was reversed to a relaxation in the presence of the H1-blocker brompheniramine. The relaxation was blocked by the H2-blocker methiamide, indicating the presence of both H1- and H2-receptors. Brompheniramine, 10-9-10-5M, delayed the onset and diminished the maximum Schultz-Dale contraction, whereas methiamide, 10-4M, increased the antigen-induced contraction without influencing the time of onset of the contraction. Diffusate from challenged and chopped guinea-pig lung contracted the lung strip. This was completely blocked by a combination of brompheniramine, 10-5M, and the SRS/A blocker FPL 55712, 10 μg/ml. However, FPL 55712 did not influence either the onset or the extent of the Schultz-Dale contraction of the lung strip. Indomethacin, 0.05-5 μg/ml, did not influence the Schultz-Dale contraction, whereas a high dose, 50 μg/ml, decreased the height of the contraction. It is concluded that the isolated lung strip of the guinea-pig is a useful in vitro model for studying the Schultz-Dale reaction. The smooth muscles contain histamine receptors of H1 and H2 type. The anaphylactic contraction, especially during the early phase, is partially mediated by histamine. The lack of evidence of SRS-A as an important mediator depends more probably on the inability of FPL 55712 to block the effect of endogenously generated SRS-A than on the lack of SRS-A receptors on the smooth muscles of the lung. © 1979 Birkhäuser Verlag.