Light exposure stimulates arachidonic acid metabolism in intact rat retina and isolated rod outer segments |
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Authors: | Dale L Birkle Nicolas G Bazan |
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Institution: | (1) Louisiana State University Eye Center, 2020 Gravier Street, 70112 New Orleans, Louisiana;(2) Eye, Ear, Nose and Throat Hospital, 70112 New Orleans, Louisiana;(3) Present address: Department of Pharmacology, West Virginia University Health Sciences Center North, 26506 Morgantown, WV |
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Abstract: | This paper presents evidence that short-term exposure to light increases synthesis of hydroxyei-cosatetraenoic acid (HETE) and prostaglandin D2 (PGD2) and stimulates the uptake and metabolism of 20 4 in phospholipids and triacylglycerols in rat retina. There was a time-dependent increase in incorporation of 1-14C-20 4 into glycerolipids in both dark-adapted and light-exposed groups. Exposure to light for 15 or 30 min enhanced the acylation of 20 4 into phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine and triacylglycerols. In the light-exposed groups there was a large increase in the conversion of 20 4 to leukotriene B4, two diHETEs, 5-HETE, 15-HETE, and PGD2. The stimulation of HETE synthesis by light could be due to early stages of light-induced lipid peroxidation in visual cells. To examine this, we studied peroxidation of 20 4 in isolated rod outer segments (ROS). There was more oxidation of 20 4 in light-exposed ROS, as compared to ROS incubated in the dark. Vitamin E and nordihydroguaiaretic acid inhibited the light-induced formation of some of these products. The data indicate that photo-oxidation of 20 4 in ROS is accompanied by enzymatic oxygenation that is stimulated by light. Increased production of HETEs and PGD2 may be a consequence of the light-induced stimulation of the metabolism of 20 4 in membrane phospholipids in the retina. |
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Keywords: | Arachidonic acid ROS phospholipids lipid peroxidation HETEs prostaglandins lipoxygenase |
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