Non-immunological release of slow-reacting substance from guinea-pig lungs.

1 During incubation with calcium ionophore A23187, sensitized and unsensitized guinea-pig chopped lung released a slow-reacting substance (SRS) and histamine. 2 SRS possessed many characteristics of slow-reacting substance of anaphylaxis (SRS-A). It was inactivated by arylsulphatase, antagonized by FPL55712 (1 microgram/ml) and more stable in alkali than acid. Furthermore, it behaved like SRS-A by stimulating archidonic acid metabolism in guinea-pig isolated perfused lungs. 3 Maximal ionophore generation of SRS in sensitized lung was greater than maximal anaphylactic generation of SRS-A but the release of histamine was not significantly different. Simultaneous challenge with antigen and ionophore produced more SRS-like or SRS-A-like activity than either stimulus alone. 4 These results have shown a non-immunological release from guinea-pig lung of SRS which was similar (or possibly identical) to SRS-A. It is suggested that in addition to mast cells, other cell types may be involved.