[Ultrastructural localization of lipid peroxides in the eye. Presentation of a new method].
Lipid peroxidation is considered a prominent feature of age-related retinal degeneration. It is known that lipid peroxides can oxidize benzidine. This property was used to localize lipid peroxides ultrastructurally in the retina.


METHODS
(1) Lipid peroxides were formed by incubation of linoleic acid with lipoxygenase from soybean, separated by thin layer chromatography and incubated with tetramethylbenzidine. (2) Lipid peroxides were formed by incubation of porcine retinae with soybean lipoxygenase in an oxygensaturated atmosphere. For ultrastructural localization, isolated retinae with and without enzymatically synthesized lipid peroxides were fixed with 2% glutaraldehyde, incubated with 0.5 mg/ml tetramethylbenzidine and embedded for electron microscopy. (3) Eye cups from Syrian golden hamsters were treated in the same way except for incubation with lipoxygenase. The hamsters were kept under constant illumination (1000 lux) for 12 h to enhance lipid peroxidation.


RESULTS
(1) Tetramethylbenzidine was oxidized by linoleic acid peroxides. (2) In the isolated retinae of pigs lipid peroxides became visible as electron-dense structures in the rod outer segments (ROS) after treatment with lipoxygenase and were lacking in the other parts of the retina. Without treatment with lipoxygenase lipid peroxides were only infrequently seen in ROS. (3) In the eyes of light-exposed hamsters, electron-dense reaction products of lipid peroxides were particularly prominent between the basal infoldings of the RPE and within the apical parts of the ROS.


CONCLUSIONS
Light or enzymatically induced lipid peroxides can be localized ultrastructurally due to their ability to react with tetramethylbenzidine and osmium in the absence of H2O2 to an electron-dense reaction product. Lipid peroxides seem to be removed from the RPE via Bruch's membrane and blood vessels. Disturbance of this pathway may enhance lipofuscin or drusen formation.
Schraermeyer
U
U
Abteilung für Netzhaut- und Glaskörperchirurgie, Augenklinik der Universität zu Köln.
Kayatz
P
P
Heimann
K
K
D000818:Animals; D001560:Benzidines; D002855:Chromatography, Thin Layer; D006224:Cricetinae; D006801:Humans; D015227:Lipid Peroxidation / Q000502:physiology*; D008054:Lipid Peroxides / Q000032:analysis*; D008647:Mesocricetus; D008854:Microscopy, Electron; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species; D012160:Retina / Q000473:pathology; D012162:Retinal Degeneration / Q000473:pathology*; D013552:Swine
D001560:Benzidines; D008054:Lipid Peroxides; D017382:Reactive Oxygen Species; C021758:3,3',5,5'-tetramethylbenzidine
Ultrastrukturelle Lokalisation von Lipidperoxiden im Auge. Vorstellung einer neuen Methode.