LONG WAVE ULTRAVIOLET RADIATION STIMULATES ARACHIDONIC ACID RELEASE AND CYCLOOXYGENASE ACTIVITY IN MAMMALIAN CELLS IN CULTURE

Human fibroblasts and mouse C3H 10T1/2 cells in culture were prelabeled with 3H]arachidonic acid and exposed to UVA radiation. Cells released labeled arachidonate metabolites into medium in a dose-dependent fashion (5-20 J cm-2). The time course of release appeared biphasic with peak responses occurring immediately and at 2 h post irradiation. Release of radiolabel was oxygen and calcium ion dependent and was inhibited by the addition of phenylglyoxal, indomethacin, and dibucaine to the medium. High performance liquid chromatographic examination of medium extracts revealed UVA stimulation of cyclooxygenase metabolism of 3H]arachidonic acid and specifically, prostaglandin E2 production by cells in culture. Furthermore, UVA stimulated a dose-dependent release of membrane incorporated 3H]choline from cells in culture. Paper chromatographic analysis of the medium provided evidence that choline release from the membrane was predominantly accompanied by release of phosphorylcholine with some glycerophosphorylcholine suggesting indirectly that the major pathway for UVA-stimulated arachidonic acid release was via phospholipase C and diacylglycerol lipase enzyme systems.