CONNEXIN DISTRIBUTION IN THE RABBIT AND RAT CILIARY BODY - A CASE FORHETEROTYPIC EPITHELIAL GAP-JUNCTIONS

Purpose. To evaluate the distribution of different alpha- and beta-typ e connexins (Cx) present in the dual layered ciliary body epithelia (C BE) of both rabbit and rat. Methods. Immunocytochemical detection of C x26, Cx32, Cx43,, and Cx50 was performed on frozen sections of rabbit and rat ciliary body using indirect immunofluorescent methods. The ide ntity of the antigens recognized by the monoclonal primary antibodies was further confirmed by Western immunoblots. Double labeling experime nts based on either conventional or confocal microscopy ere carried ou t to establish the exact spatial relationship between different connex ins. Results, Connexin 50 was found only in the nonpigmented epitheliu m (NPE) at apical and basolateral membranes, whereas Cx43 was observed exclusively and at a very high concentration in the pigmented epithel ium (PE), primarily in the apical cell membrane, with minimal extensio n to the proximal lateral zone. The correct antigenicity of the antibo dies was confirmed by Western blots of rabbit ciliary body membranes. In rabbit, the Cx26 antibody detected an antigen that was abundant in the NPE and was weakly expressed in the PE. In rat, however, the Cx26 staining was confined to capillary wall endothelia. Western blots of c iliary body and liver membranes and liver immunohistology indicated th at the Cx26 antibody used does not recognize rabbit Cx26. Cx32 did not yield any substantial epithelial labeling in either species. Conclusi ons. The distribution of Cx50 around the entire NPE cell perimeter sug gests its involvement in NPE-NPE cell homotypic gap junctions. The con centration of Cx43 and Cx50 at the apical membranes of the PE and NPE cells, respectively, and their complete absence from the opposite cell suggest that these connexins may participate in the formation of hete rotypic gap junctions, either with each other or with other yet uniden tified connexins.