SLOW REACTING SUBSTANCE AS A PREFORMED MEDIATOR FROM HUMAN LUNG

  • 1 January 1976
    • journal article
    • research article
    • Vol. 31  (5) , 813-820
Abstract
Homogenates from human lung contained a preformed slow reacting substance (pSRS). The pattern of contraction on the guinea-pig ileum by pSRS was indistinguishable from that of SRS-A [slow reacting substance of anaphylaxis]. The activity of pSRS could not be attributed to the presence of K+, Na+, Ca2+ and Mg2+, or any prostaglandin including PGF2.alpha. or its 15-oxo derivative. As with SRS-A, pSRS could be adsorbed onto Amberlite XAD-2 and silicic acid. Both were eluted from the former with 80% ethanol and from the latter with a mixture of ethanol, ammonia and water. SRS-A and pSRS were resistant to the action of NaOH, whereas their activities were destroyed by boiling in HCl. Arylsulfatase II B destroyed the activities of pSRS and SRS-A. An antagonist of SRS-A, FPL 55712, inhibited the action of pSRS at comparable concentrations to that of SRS-A. pSRS and SRS-A are probably identical. SRS joins histamine and ECF-A [eosinophil chemotactic factor of anaphylaxis] as a preformed mediator. Although SRS was present in a preformed state, the amount of material extractable was more than doubled by the anaphylactic reaction. The extraction of pSPS from human lung without apparent requirement for antigen or antibody points to a possible role of this mediator in inflammatory reactions evoked by mechanisms independent of IgE [immunoglobulin E] and other tissue-sensitizing antibodies.