Tritiated uridine labeling of the retina: variations among retinal quadrants, and between right and left eyes

We have determined the pattern of RNA labeling (uridine incorporation) in the normal retina of the domestic cat. One eye in each of eight cats was labeled by injecting [3H]uridine into the vitreous cavity. Two of the labeled eyes had the lens and vitreous removed 10 days before labeling. Three additional animals received intravenous (i.v.) injections of [3H]uridine. All animals were injected 4 hr into the light period and fixed 24 hr later; then the retinas were divided into quadrants (ST = superior temporal, SN superior nasal, IT = inferior temporal, and IN = inferior nasal). The ST quadrant contains the area centralis and the SN quadrant the optic nerve head. Autoradiograms were prepared from plastic sections 1 micron thick taken near the centre of each quadrant. In animals receiving intravitreal [3H]uridine, the ganglion cells and the inner and outer nuclear layers (INL; ONL) were heavily labeled; the synaptic layers and the retinal pigment epithelium (RPE) were very lightly labeled. Amacrines were the heaviest labeled cells in the INL; cones were more heavily labeled than rods in the ONL. This finding indicates that amacrines and cone photoreceptors may be synthesizing RNA more actively than other retinal neurons. In animals receiving intravenous [3H]uridine the pattern of labeling was the same as above except that the RPE was heavily labeled. Because cells in the ST quadrant appeared to be more heavily labeled than the same cell types in the other retinal quadrants, silver grains over the ONL in each quadrant were counted as grains micron -2 or grains per rod nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)