Immunocytochemical and electrophoretic distribution of cytokeratins in the resting stage epidermis of the lizard Podarcis sicula.

The distribution of three anti-cytokeratin (alpha-keratin) antibodies (AE1, AE2, AE3) in the epidermis of a lizard has been studied by immunocytochemistry at light and electron microscope and by immunoblot analysis. This study shows the expression of different keratins in the resting stage epidermis of the lizard Podarcis sicula. In this stage the epidermis has an external beta-layer, an underlying alpha-layer, some layers of living suprabasal cells and a basal stratum germinativum. The AE1 antibody is localized in the basal and suprabasal cells only in the outer scale surface, but is absent from the inner surface, the hinge region and from the keratinized beta- and alpha-layers. The AE2 antibody is mainly localized at the level of the hinge region and of the alpha-layer and gives a lower reaction in the beta-layer. The AE3 antibody is mainly localized in basal and suprabasal cells, lower in the alpha-layer, and absent from the beta-layer. The electron microscope shows that all the three antibodies immunolabel cytoplasmic fibrillar structures in the deep alpha-layers and that AE2 and AE3 antibodies label small electron-dense areas in the external dense beta-layer within the electron-lucid matrix. Immunoblot analysis of the keratins extracted and separated by gel electrophoresis demonstrates the presence of a band of high molecular weight (67-68 kDa) positive to all three antibodies. In addition AE1 antibody recognizes a 44-45 kDa band and a 57-58 kDa band, AE2 recognizes a 60-61 kDa band, and AE3 recognizes a 47 kDa and a 56-57 kDa band. The localization of the keratins identified by immunoblot analysis in the epithelial layers is discussed taking in account the immunolabeling at light and electron microscope. The present study suggests that also in the normal epidermis of this reptiles, in both the alpha- and the beta-layer, the molecular masses of keratins increase from the basal to the keratinized layers, a phenomenon which is generalized to adult and embryonic amniotes epidermis.