SECRETORY PHOSPHOLIPASE A(2) ACTIVITY IS ELEVATED IN BRONCHOALVEOLAR LAVAGE FLUID AFTER OVALBUMIN SENSITIZATION OF GUINEA-PIGS

Arachidonic acid (AA), the precursor of eicosanoids, is released from the sn-2 position of phospholipids by both secretory (sPLA(2)) and cyt osolic phospholipase A(2) (cPLA(2)), Eicosanoids have been shown to co ntribute to bronchospasm in asthma, We measured the enzymatic activity of sPLA(2) and cPLA(2) in the bronchoalveolar lavage fluid and cells, respectively, in male Wartley guinea pigs sensitized with ovalbumin, sPLA(2) activity was also measured from alveolar macrophages (AM) in c ulture from unsensitized and sensitized animals, There was an increase in sPLA(2) activity and AA content in the lavage fluid following sens itization (18.73 +/- 1.33 to 25.74 +/- 3.22% hydrolysis and 17.97 +/- 12.39 to 44.76 +/- 13.37 pmol AA/mL BAL, mean +/- SD), which remained elevated but without further increase 4 or 24 h after antigen challeng e. AM from unsensitized and sensitized-unchallenged animals did not se crete sPLA(2) activity in culture for 3 h and therefore do not appear to be the cell source of the sPLA(2) activity present in the alveolar lavage fluid following OA sensitization, In contrast to the increase i n sPLA(2) in lung lavage fluid, Western blotting for cPLA(2) from lung lavage cells showed no increase 4 or 24 h after antigen challenge com pared with sensitization alone, cPLA(2) enzymatic activity of the cyto sol fraction of lung lavage cells showed no changes with antigen sensi tization or challenge, In summary, intraperitoneal sensitization with ovalbumin in male Hartley guinea pigs caused an increase in both sPLA( 2) and AA in bronchoalveolar lavage fluid without a need for antigen c hallenge, The increased sPLA(2) enzymatic activity following sensitiza tion may be responsible for the elevation of AA in the bronchoalveolar lavage fluid observed after antigen sensitization.