DISTRIBUTION OF CONNEXIN43 IMMUNOREACTIVITY IN THE RETINAS OF DIFFERENT VERTEBRATES

The distribution of Connexin43 (Cx43) was examined by immunoblotting a nd immunofluorescence microscopy in the retinas of five different vert ebrates by using a C-terminal specific peptide antibody. The specifici ty of the antibody was proved on immunoblots, in which it showed cross reactivity with a 43-kDa protein in rat heart homogenates as well as in homogenates of rabbit, rat, chicken, turtle, and fish (carp and zeb rafish) retinas. Immunofluorescence histochemistry with retinal cryose ctions revealed the presence of Cx43 in the retinal pigment epithelium cells of all tested species and in blood vessels of vascularized reti nas (fish and rat). Cx43 immunoreactivity was further localized in the stria medullaris of rabbit retina, in the nerve fiber layer of rat re tina, most likely in astrocytes, and in the area of the outer limiting membrane of the fish retina, most likely representing Cx43 in Muller glia cells. A punctate Cx43 immunoreactive pattern consistent with gap junctions was also detected in the outer plexiform layer of carp and zebrafish retinas, and a specific amacrine cell type, which ramified i n two layers of the inner plexiform layer, was labeled in the zebrafis h retina. The present results are in accordance with previous findings showing the abundance of Cx43 in astrocytes, endothelium, and epithel ial cells. However, the presence of Cx43 immunoreactivity in a specifi c population of amacrine cells of the zebrafish retina might indicate that a Cx43-like protein is also expressed in neurons. (C) 1998 Wiley- Liss, Inc.