Total profiling by GC/NICIMS of the major cyclo-oxygenase products from antigen and leukotriene-challenged guinea-pig lung

Abstract

Separation and quantitation of all the major cyclo-oxygenase products in perfused guineapig lungs challenged with antigen or leukotrienes C 4 and D 4 were achieved using a novel combined capillary column gas chromatography/negative ion chemical ionization mass spectrometric (GC/NICIMS) method. In descending order of magnitude, unchallenged lungs released thromboxane B 2 (TXB 2) plus its pulmonary metabolite (TXDK) > 6-keto-PGF 1 α plus its 13,14-dihydro-15-keto metabolite (K 2H 1F 1 α ) > PGE 2 plus PGF 2 α > PGD 2; after ovalbumin anaphylaxis there were increases of TXB 2 plus TXDK, ×28 in PGD 2 and histamine (measured fluorometrically) but of only ×3 in 6-keto-PGF 1α plus K 2H 2F 1α and PGE 2 plus PCF 2α. FPL55712 treatment greatly reduced the release of TXB 2 and 6-keto-PGF 1α and their metabolites (showing this to be a secondary effect mediated by leukotriene action) but did not affect PGD 2 output. LTC 4 and LTD 4 themselves induced the release of TXB 2 and TXDK, as did bradykinin, but neither substance caused appreciable PGD 2 release. Aside from illustrating the great value of the GC/NICIMS method for simultaneously determining all cyclo-oxygenase products, the main conclusions are: (i) PGD 2 may be an in vitro marker for activation of lung inflammatory cells; (ii) prostacyclin and thromboxanes are actively metabolized in situ in the lung; and (iii) ‘pathological subversion’ of pulmonary function by anaphylaxis, leukotrienes or bradykinin principally causes thromboxane release from unknown target cells, with a smaller release of prostacyclin which may be compensatory in nature.