Background: It is now well known that to counteract oxidative stress and maintain a redox balance within the cells, the skin is equipped with a network of antioxidant enzymes. Among these enzymes, SOD and CAT are the major antioxidant enzymes protecting the epidermis.
Objective: In the present study, we have attempted to demonstrate the distribution of endogenous H(2)O(2) and the expression of CAT in the epidermis of newborn rats, in relation to epidermal differentiation, and alterations after UVB irradiation.
Methods: We have localized the antioxidant enzyme catalase (CAT) using immunohistochemical analysis, and hydrogen peroxide (H(2)O(2)) using in situ H(2)O(2) assay.
Results: We demonstrated that keratinocytes in the stratum granulosum produced H(2)O(2), and CAT was mainly expressed in the cytoplasm of cells from the stratum granulosum to the lower corneum, and in the cell periphery in the stratum granulosum of newborn rat skin. The results suggested that generation of H(2)O(2) and expression of CAT were coordinated and were indicative of epidermal differentiation as well as of the role of CAT in repairing redox damage by discomposing H(2)O(2). When rat skin was exposed to 50 mJ/cm(2) of ultraviolet B (UVB) rays, the accumulation of H(2)O(2) in the upper epidermis increased twenty-four hours later, while CAT immunoreactivity decreased.
Conclusion: The results suggested that generation of H(2)O(2) and expression of CAT were coordinated and were indicative of epidermal differentiation as well as of the role of CAT in repairing redox damage by discomposing H(2)O(2). In addition, UVB-induced oxidative stress in the present study seemed to alter the endogenous and differentiation-specific redox balance between H(2)O(2) and CAT.