Light exposure stimulates arachidonic acid metabolism in intact rat retina and isolated rod outer segments.
This paper presents evidence that short-term exposure to light increases synthesis of hydroxyeicosatetraenoic 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 an PGD2 may be a consequence of the light-induced stimulation of the metabolism of 20:4 in membrane phospholipids in the retina.
Birkle
D L
DL
Louisiana State University Eye Center, New Orleans.
Bazan
N G
NG
D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism* / Q000528:radiation effects; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism*; D066298:In Vitro Techniques; D008027:Light; D008297:Male; D010743:Phospholipids / Q000096:biosynthesis; D010786:Photoreceptor Cells / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012160:Retina / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D014280:Triglycerides / Q000096:biosynthesis
D001095:Arachidonic Acids; D006893:Hydroxyeicosatetraenoic Acids; D010743:Phospholipids; D014280:Triglycerides