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Cellular localization of glutathione S-transferases in retinas of control and lead-treated rats
S McGuire1, D Daggett, E Bostad
1Department of Neurology, University of Wisconsin, Madison, WI 53705, USA.
Purpose:
The glutathione S-transferases (GSTs) constitute a family of cytosolic isoenzymes that are involved in the detoxication of electrophilic 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 damage by lead and other toxicants.
Methods:
The regional and cellular distribution of cytosolic GSTs in rat retina of control and lead-treated animals was studied by immunohistochemistry. Enzyme activity was determined by a spectrophotometric assay. The GST subunit distribution of the entire retina of control and lead-treated animals was determined and quantified by reverse-phase high-performance liquid chromatography (HPLC).
Results:
Polyclonal antibodies against mu-class Yb1 and Yb2 GSTs were primarily and strongly reactive with Müller cells and their processes. Anti-Yb1 also reacted with photoreceptor outer segments. Antibodies against two alpha-class GSTs (Ya and Yk) were strongly reactive with Müller cells and their cell processes. Antibodies against Yp and Yc GSTs were reactive with amacrine cells and their processes, and anti-Yp antibodies were reactive against retinal ganglion cells. Treatment of rats with triethyl lead caused diminished reactions of the antibodies against Yb1 and Yp GSTs and increased reactions of anti-Ya with its retinal targets, whereas the total GST activity did not change significantly.
Conclusions:
The positive reaction between the amacrine neuronal cells of retina and the anti-Yp and anti-Yc class antisera broadens the class of neurons that contains GST enzymes protective against toxicant insult. It also has been shown that Müller cells are strongly immuno-positive for Yb1 and Yb2 GST. Because these phagocytic cells are in contact with the vitreous fluid and proximate to pigmented epithelial layer of the eye, these GSTs may protect the cells from toxicants accumulated from this fluid.