CYTOKERATIN-FILAMENT EXPRESSION IN EPITHELIAL AND NONEPITHELIAL TISSUES OF THE COMMON CARP (CYPRINUS-CARPIO)

Cytokeratin expression in mammals is generally restricted to epithelia l cells and has been utilized to differentiate epithelial from nonepit helial tissues in these species. Since cytokeratins have been shown to be highly conserved during vertebrate evolution, the objective of the present study has been to ascertain the expression pattern of cytoker atins in tissues of the common carp (Cyprinus carpio). A panel of 10 a nti-human cytokeratin antibodies was evaluated using a streptavidin-bi otin-peroxidase complex detection system. Tissues were fixed in 10% ne utral-buffered formalin, 100% ethanol or methacarn. Only formalin-fixe d tissues were pre-digested with trypsin prior to immunostaining. Form alin-fixed tissues generally resulted in a less intense, more diffuse staining pattern with considerable background compared with ethanol an d methacarn and was therefore the least desirable fixative. The divers e staining pattern observed with the various antibodies used in this s tudy was consistent with previous findings in other teleosts. The resu lts confirm that cytokeratin expression in teleosts is fundamentally d ifferent from that in mammals and therefore should be used as a method to differentiate epithelial cell types in these species only with dis cretion.