Presence of acid phosphatase in the epidermis of the regenerating tail of the lizard (Podarcis muralis) and its possible role in the process of shedding and keratinization

The activity and distribution of the lysosomal marker enzyme acid phosphata se have been studied in the epidermis during tail regeneration in the lizar d Podarcis muralis. This study gives information both on the mechanism of s eparation of the old from the new epidermal generation and on the involveme nt of lysosomes in beta- and alpha-keratinization in lepidosaurians. The bi ochemical analysis shows that the activity of acid phosphatase was higher i n the regenerating tail than in the normal tail until the stage of skin she dding at around 25-30 days post-amputation. The enzyme was present in kerat inizing layers of epidermis, and particularly in the shedding layer. The sh edding layer followed the outline of the regenerating scales beneath the wo und in the epidermis showing that lysosomal enzymes are involved in epiderm al shedding. The ultrastructural study showed that acid phosphatase was ini tially localized within the lysosomes but, with the progress of differentia tion, it also appeared free within the cytoplasm of the cornifying cells of the shedding complex and of the beta-keratinizing cells, and in the interc ellular space among them. The role of lysosomal enzymes in the shedding pro cess and their involvement in the mechanism of beta-keratinization is discu ssed. While the process of beta-keratinization has an intracellular and ext racellular localization of acid phosphatase, the process of alpha-keratiniz ation shows that most acid phosphatase is localized within the cell. Lysoso mes and mesos granules containing acid phosphatase were concentrated in the cytoplasm of differentiating mesos cells. Some mesos granules later discha rged their contents into the extracellular space. The alpha-layer was parti ally formed in proximal regenerated scales around 30 days post-amputation. Lysosomes appeared to concentrate within pre-keratinizing cells of the alph a-keratin layer and little reactivity was seen extracellularly.