Slow Reacting Substance and Related Compounds

Abstract

Slow reacting substance A (SRS-A) is an acidic substance produced in most tissues during antigen-antibody reactions of immediate type. Lung from human asthmatic subjects gives a good yield of this substance when challenged with the appropriate antigen in vitro, and since SRS-A can cause a strong and well-maintained contraction in isolated human bronchioles, it is presumed to play an important role in asthma. Other possible actions cannot be detected satisfactorily until larger and purer samples are produced. SRS-A has not been obtained in a pure state, and the impurities probably modify the chemical and physical properties of the active substance. The fragments of information available suggest that it acts by forming complexes with lipids of cell-membranes, although it does not itself have properties typical of a lipid. No potent and relatively specific antagonist has been found so far, but even relatively weak antagonists appear to produce worthwhile improvements in asthmatic states.