Constitutive and inducible heat shock protein 70 immunoreactivity in the normal rat eye

Distributions for the constitutive and inducible 70-kDa heat shock proteins, Hsc70 and Hsp70, in different parts of the rat eye are likely to be related to the metabolic demands required for absorption and detection of light. This study was conducted to better understand the functions of Hsc70 and Hsp70 in these tissues and to provide a basis for elucidating their contributions to the maintenance and repair of ocular structures subsequent to tissue injury or cellular degeneration.

Eyes from male Sprague-Dawley rats (200-300 g) were fixed in methacarn and embedded in paraffin. Sagittal sections (10 microm) through the optic nerve were stained with hematoxylin and eosin or incubated with heat shock protein antibody or control IgG. Bound antibody was visualized using an avidin- biotin- horseradish peroxidase detection system.

Hsc70 immunoreactivity was detected in all layers of the retina, except the outer segments. In the retinal pigment epithelium, staining was restricted to cells near the optic nerve-retina junction. Intense staining was also observed in glial nuclei of the optic nerve, whereas weaker staining was observed in the basal and wing cells of the limbal and corneal epithelia. In contrast, Hsp70 immunoreactivity was restricted to the outer nuclear layer and inner segments of the retina. Hsp70 staining was also prominent in basal and wing cells of the limbal cornea and to a lesser extent in the central corneal epithelium. The optic nerve was Hsp70 negative.

Hsc70 and Hsp70 have distinct distributions in the normal rat eye, which imply regional and cell-specific functions.