Patterns of cytokeratins and lamins in rat liver and in rat liver cell lines as shown by immunoblotting using the monoclonal antibodies A 45-B/B3 and A 51-B/H4.

The cytokeratins and lamins of rat liver nuclei, nuclear lamina, and cytoskeleton preparations as well as of rat liver cell lines were studied by immunoblotting using the monoclonal broad-range cytokeratin antibodies A 45-B/B3 and A 51-B/H4. A 45-B/B3 is bound to 64-, 58-, 55-, 52.5-, 49-, 45-, 43-, 39-, and 35-kDa proteins, which are already known as rat liver cytokeratins, excepted the 64- and 35-kDa bands. This antibody can therefore be considered to be a pan-cytokeratin marker for the rat. A 51-B/H4 detected an epitope occurring in both lamins (70, 67, and 60-63 kDa) and cytokeratins (49, 45, 43, and 39 kDa). In a few experiments, this monoclonal antibody also indicated a 55-kDa protein. Furthermore, in some cell lines a 80-kDa protein was detected which possibly may correspond to a higher molecular member of the lamin family. In subcellular preparations, the full set of cytokeratins was found to be associated with the nuclei and the nuclear lamina fraction, suggesting a tight connection of the intermediate filaments with the nuclear lamina. Cell lines derived from fetal or neonatal rat liver exhibited cytokeratin patterns which resembled the phenotype of immature or atypically differentiated parenchymal liver cells.