Tritiated uridine labeling of the retina: changes after retinal detachment

As part of a study designed to examine the response of photoreceptor cells to outer segment injury (retinal detachment), the pattern of RNA labeling ([3H]uridine incorporation) has been determined in detached cat retinas. Retinas were experimentally detached from the adjacent cellular layer (the retinal pigment epithelium:RPE) by injecting fluid into the extracellular space between the retina and RPE. Twenty-four hours before the animals were killed they received intravitreal injections of [3H]uridine. Autoradiograms were prepared from plastic sections 1.0 micron thick taken from detached retinal regions and, because the detachments do not encompass all of the retina, from nearby attached retinal regions. Twenty-four hours after retinal detachment there is a decrease in labeling intensity of the photoreceptors and Müller's glia in the region of detachment (compared to cells in nearby attached regions). Seventy-two hours after retinal separation, the same result is obtained in the photoreceptors, but labeling intensity is greatly increased in both the nuclei and cytoplasm of Müller's glia. The decrease in [3H]uridine labeling of the photoreceptors correlates with a decreased staining intensity of the cytoplasm and ultrastructural signs of necrosis. The striking change in the pattern and intensity of labeling of the Müller cells precedes extensive hypertrophy of these cells and the appearance within their cytoplasm of numerous 10-nm diameter filaments. Two weeks, and also 1 month, after detachment the pattern and labeling levels are similar to those observed 1 day after retinal separation. These data suggest a highly localized change in metabolism because the change in RNA labeling is restricted to the region of detached retina.