CALCIUM-DEPENDENT RELEASE OF ARACHIDONIC-ACID IN RESPONSE TO PURINERGIC RECEPTOR ACTIVATION IN AIRWAY EPITHELIUM

The effect of purinergic receptor agonists on arachidonic acid release was investigated in [H-3]arachidonic acid-prelabeled human airway epi thelial cells. Exposure of bronchial epithelial BEAS39 cells to extrac ellular ATP resulted in a marked release of unesterified [H-3]arachido nic acid with maximal effect observed within 60-90 s. [H-3]diacylglyce rol and [H-3]phosphatidic acid accumulated in parallel with [H-3]arach idonic acid. ATP-stimulated [H-3]arachidonic acid release with a K-0.5 of 9 +/- 2 mu M and UTP was equipotent; no effect was observed with P -2Y- or P-2X-purinergic receptor agonists or with adenosine. Similar r esults were obtained with primary cultures of normal human nasal epith elium, CF/T43 and HBE1 airway epithelial cell lines derived from a cys tic fibrosis patient and from a normal donor, respectively, and HT-29 human colon carcinoma cells. ATP stimulated inositol phosphate formati on in BEAS39 cells with a concentration dependence identical to that f or [H-3]arachidonic acid release. The effect of ATP on both [H-3]arach idonic acid release and inositol phosphate formation was equally inhib ited by pertussis toxin. The Ca2+ ionophore A-23187 mimicked the effec ts of ATP or UTP on arachidonic acid release, and a marked inhibitory effect was observed with thapsigargin. The protein kinase C inhibitor staurosporine partially inhibited ATP-stimulated [H-3]arachidonic acid release. These data are consistent with the hypothesis that phospholi pase A(2) activation is secondary to P-2U-purinergic receptor stimulat ion of D-myoinositol 1,4,5-trisphosphate production and calcium mobili zation from intracellular stores.