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(Arteriosclerosis, Thrombosis, and Vascular Biology. 1997;17:295-299.)
© 1997 American Heart Association, Inc.

Articles

Involvement of Phosphatidylcholine Hydrolysis by Phospholipase D in Extracellular ATP-Induced Arachidonic Acid Release in Aortic Smooth Muscle Cells

Junji Shinoda; Atsushi Suzuki; Yutaka Oiso; Osamu Kozawa

the First Department of Internal Medicine, Nagoya University School of Medicine, (J.S., A.S., Y.O.); and the Department of Biochemistry, Institute for Developmental Research, Aichi Human Service Center, Kasugai (O.K.), Japan. Dr Kozawa is now with the Department of Pharmacology, Gifu University School of Medicine, Japan.

Correspondence to Osamu Kozawa, MD, PhD, Department of Pharmacology, Gifu University School of Medicine, Gifu 500, Japan.

We investigated the effect of extracellular ATP on phosphatidylcholine-hydrolyzing phospholipase D activity and the role of phospholipase D activation in extracellular ATP-induced arachidonic acid release in cultured rat aortic smooth muscle cells. ATP significantly stimulated the formation of choline in a dose-dependent manner in the range between 0.01 and 0.5 mmol/L. However, ATP had no effect on the formation of phosphocholine. Staurosporine, an inhibitor of protein kinases, did not affect the ATP-induced formation of choline. ATP significantly stimulated arachidonic acid release in a dose-dependent manner in the range between 0.01 and 0.5 mmol/L. DL-Propranolol hydrochloride (propranolol), an inhibitor of phosphatidic acid phosphohydrolase, significantly inhibited the ATP-induced release of arachidonic acid. 1,6-Bis(cyclohexyloximinocarbonylamino)-hexane (RHC-80267), a potent and selective inhibitor of diacylglycerol lipase, reduced ATP-induced arachidonic acid release. Quinacrine, a phospholipase A₂ inhibitor, suppressed ATP-induced arachidonic acid release. Both propranolol and RHC-80267 markedly inhibited the ATP-induced synthesis of 6-ketoprostaglandin F₁, a stable metabolite of prostacyclin. These results strongly suggest that extracellular ATP activates phosphatidylcholine-hydrolyzing phospholipase D independently of protein kinase C in aortic smooth muscle cells and that the arachidonic acid release induced by extracellular ATP is mediated, at least in part, through phosphatidylcholine hydrolysis by phospholipase D activation.

Key Words: extracellular ATP • phosphatidylcholine • phospholipase D • arachidonic acid • aortic smooth muscle cells