CELLULAR-LOCALIZATION OF GLUTATHIONE S-TRANSFERASES IN RETINAS OF CONTROL AND LEAD-TREATED RATS

Purpose. The glutathione S-transferases (GSTs) constitute a family of cytosolic isoenzymes that are involved in the detoxication of electrop hilic xenobiotics. The purpose of this investigation was to determine the concentration and cellular distribution of the various classes of cytosolic GSTs in the retina of control and triethyl lead-treated rats and thereby reveal mechanisms by which the cells are protected from d amage by lead and other toxicants. Methods. The regional and cellular distribution of cytosolic GSTs in rat retina of control and lead-treat ed animals was studied by immunohistochemistry. Enzyme activity was de termined by a spectrophotometric assay. The GST subunit distribution o f the entire retina of control and lead-treated animals was determined and quantified by reverse-phase high-performance liquid chromatograph y (HPLC). Results. Polyclonal antibodies against mu-class Yb-1 and Yb- 2 GSTs were primarily and strongly reactive with Muller cells and thei r processes. Anti-Yb, also reacted with photoreceptor outer segments. Antibodies against two alpha-class GSTs (Ya and Yk) were strongly reac tive with Muller cells and their cell processes. Antibodies against Yp and Yc GSTs were reactive with amacrine cells and their processes, an d anfi-Yp antibodies were reactive against retinal ganglion cells. Tre atment of rats with triethyl lead caused diminished reactions of the a ntibodies against Yb-1 and Yp GSTs and increased reactions of anti-Ya with its retinal targets, whereas the total GST activity did not chang e significantly. Conclusions. The positive reaction between the amacri ne neuronal cells of retina and the anti-Yp and anfi-Yc class antisera broadens the class of neurons that contains GST enzymes protective ag ainst toxicant insult. It also has been shown that the Muller cells ar e strongly immunopositive for Yb-1 and Yb-2 GST. Because these phagocy tic cells are in contact with the vitreous fluid and proximate to pigm ented epithelial layer of the eye, these GSTs may protect the cells fr om toxicants accumulated from this fluid.