Tissue inactivation of slow reacting substance of anaphylaxis

The release of slow reacting substance of anaphylaxis (SRS-A) from sensitized guinea-pig lung challenged with antigen was followed by a fall in the activity of this mediator in the diffusate when the incubations were continued for 3 h. The inactivating principle was also present in normal lung in addition to other normal guinea-pig tissues such as the liver, kidney, spleen, ileum and skin. No acitivity was found in muscle. Evidence is provided that some of this SRS-A-inactivating activity was due to tissue arylsulphatases. These were measured by hydrolysis of p-nitrophenyl sulphate (p-NPS) and p-nitrocatechol sulphate (p-NCS), which reflect activities of arylsulphatase II A and II B respectively. Hydrolytic activity for p-NCS was present in all tissues with SRS-A-inactivating properties, whereas only lung, liver and skin tissue hydrolysed p-NCS and p-NPS. Following passage of a cell-free lung homogenate through a column of Sephadex G-200 the p-NCS hydrolysing and SRS-Z-inactivating activities eluted together, with molecules having a molecular size of approximately 150,000 Daltons, p-NPS hydrolysing activity being destroyed during the preparation of the homogenate. The release of arylsulphatase from sensitized tissue was not dependent on the presence of specific antigen. These experiments suggest that inactivation of SRS-A is related to tissue arylsulphatase and that these enzymes may play a role in the expression of the effective levels of this mediator within the tissues.