Immunocytochemical localizations of cytosolic and mitochondrial glutamic oxaloacetic transaminase isozymes in rat retina as markers for the glutamate-aspartate neuronal system.

The localization of cytosolic (s) or mitochondrial (m) glutamic oxaloacetic transaminase (GOT) was examined in the rat retina by means of an indirect immunofluorescence method using antibodies specific for s- and m-GOT. The m-GOT-like immunoreactive structures were seen on the inner segments of the photoreceptor cells and other outer and inner plexiform layers. These structures were dot-like in appearance. Somas were not labeled. In contrast, s-GOT-like structures were found on the inner segments and inner fibers of the photoreceptor cells, numerous cell somas in the inner nuclear layer (horizontal, amacrine and bipolar cells), and ganglion cell layer (displaced amacrine cells) and inner plexiform layer. The difference in distribution between s- and m-GOT isozymes suggests that they may be useful as markers for glutamatergic and/or aspartinergic neurons.