Measurement of SRS-A activities in plasma of asthmatic patients

Ethanol extracts of arterial blood from 20 of 29 asthmatic patients during attacks produced sustained contractions of the guinea pig ileum. These contractions were inhibited by FPL 55712, a specific antagonist of slow reacting substance of anaphylaxis (SRS-A). SRS-A activity was significantly higher during attack than during remission. Reverse-phase high pressure liquid chromatography (HPLC) was performed on two extracts which had shown high SRS-A activity with bioassay. One extract showed double peaks, which had retention times identical to those of leukotriene (LT) C4 and LTD4. The other extract showed a single peak, which had a retention time identical to that of synthetic LTC4.