EICOSANOID PRODUCTION IN RABBIT TRACHEAL EPITHELIUM BY ADENINE-NUCLEOTIDES - MEDIATION BY P-2-PURINOCEPTORS

Adenosine triphosphate (ATP) acting through epithelial nucleotide receptors exerts multiple physiologic actions on airway mucociliary clearance and caliber. However, the effect of ATP on arachidonate metabolism in the airway remains unknown, In this study, the ability of ATP to regulate eicosanoid production was studied in vitro in full-thickness rabbit tracheal strips and separately in rabbit epithelial explant cultures, In the freshly isolated strips, ATP increased prostaglandin E(2) (PGE(2)) release in a dose-dependent fashion, with an activation threshold at 10 mu M ATP and a 3.5-fold increase in PGE(2) output at 1 mM ATP. Epithelium removal decreased 1 mM ATP-evoked PGE(2) release by 68%. Reverse-phase, high-pressure liquid chromatography (HPLC) of media from H-3-arachidonic acid-incubated epithelial explants exposed to 1 mM ATP demonstrated increased output of the cyclooxygenase products PGE(2) and prostaglandin F-2a (PGF(2a)). Other identifiable eicosanoids did not increase, The concentration-response for ATP-induced PGE(2) release by explants was similar to that of tracheal strips. PGE(2) release by 1 mM ATP was 27% of that elicited by ionomycin (10 mu M) and was markedly inhibited by indomethacin (10 mu M). Purinoceptor agonist-stimulated PGE(2) release by the epithelium yielded a rank order of potency of uridine triphosphate (UTP) greater than or equal to ATP > 2-methylthio-ATP (2MeSATP) >> alpha,beta-methyleneadenosine-5'-triphosphate (AMP-CPP) greater than or equal to adenosine. These results indicate that ATP, acting primarily through an epithelial P-2-purinoceptor similar to the P-2u subtype, stimulates eicosanoid metabolism in rabbit airway epithelium via the cyclooxygenase pathway, producing PGE(2) as the predominant species.