Immunohistochemical study of caveolin-1 and -2 in the rat retina

Abstract

The expression of caveolin-1 and -2 in the retina was examined; Western blot analysis showed that both were present. Immunohistochemistry indicated that caveolin-1 was expressed in the majority of retinal layers, including the ganglion cell layer, inner plexiform layer, outer plexiform layer, and in the vascular endothelial cells of the retina. Caveolin-2 was primarily immunostained in the vessels, but in a few other elements as well. This is the first demonstration of caveolin differential expression in the retina of rats, and suggests that caveolin plays an important role in signal transduction in glial cells and neuronal cells.

Fig. 1

Identification of caveolin-1 and -2 in the rat retina. Protein (40 µg) from heart and retina homogenates of adult rats were separated by SDS-PAGE (12%), and then immunoblotted with caveolin-1 (A) and caveolin-2 (B) antibodies, respectively. Beta-actin was used as a control. Molecular weight markers are indicated on the right. Blots are representative of data from a series of four different preparations yielding identical results.

Fig. 2

Immunohistochemical labeling of caveolin-1 in the rat retina. Caveolin-1 was expressed in some glial cells (arrowheads), vascular endothelial cells (arrows), and was diffusely stained in the inner plexiform layers, inner nuclear layer, outer plexiform layer, and external limiting layer (A). Some ganglion cells were immunopositive for caveolin-1 (C, arrows). In the inner nuclear layer, caveolin-1 was immunostained in some neuronal cells, identical to amacrine cells (arrowhead) and bipolar cells (arrow) in morphology and location (D). In the outer nuclear layer, caveolin-1 was weakly detected in some photoreceptor cellular membranes (E, arrow), and inner segments of rods and cones (F, arrow). No reaction product was seen in sections incubated with non-immune sera (B). Counterstained with hematoxylin. The retinal layers are indicated on the right side of the retinal section (B); ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), layer of rods and cones (RCL). Scale bars: in A and B, 30 µm; in C-F, 10 µm.

Fig. 3

Immunohistochemical labeling of caveolin-2 in the rat retina. Caveolin-2 was typically immunostained in vessels of the retina (arrow), while weak staining was seen in the processes of glial cells (arrowhead) (A). Caveolin-2 was diffusely stained in the inner plexiform layer (B). Caveolin-2-immunostaining was found in the process of glial cells, identical Muller cells in morphology and location (C, arrow). Caveolin-2 was diffusely immunostained in outer plexiform layer (D, arrowhead), but limited in the inner and outer segments of rods and cones (D, arrow). Counterstained with hematoxylin. The retinal layers are indicated on the right side of the retinal section (A); ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), layer of rods and cones (RCL). Scale bars: in A, 30 µm; in B-D, 10 µm.