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Cyclo‐oxygenase metabolizes arachidonic acid to prostaglandin H₂ (PGH₂) and exists in at least two isoforms. Cyclo‐oxygenase‐1 (COX‐1) is expressed constitutively whereas COX‐2 is induced by lipopolysaccharide (LPS) and some cytokines in vitro and at the site of inflammation in vivo. Epithelial cells may be an important source of prostaglandins in the airways and we have, therefore, investigated the expression of COX‐1 or COX‐2 isoforms in primary cultures of human airway epithelial cells or in a human pulmonary epithelial cell line (A549).

COX‐1 or COX‐2 protein was measured by western blot analysis using specific antibodies to COX‐2 and selective antibodies to COX‐1. The activity of COX was assessed by the conversion of either endogenous or exogenous arachidonic acid to four metabolites, PGE₂, PGF_2α, thromboxane B₂ or 6‐oxo PGF_1α measured by radioimmunoassay. Thus, COX‐1 or …