Immunhistochemischer Nachweis von Sulfhydryloxidase und Katalase während der prä- und postnatalen Entwicklung der Rattenhaut

Keratinization is a highly complex process which leads in the end to a physical barrier for the organism. Post-translational modifications of epidermal proteins help to maintain the structural integrity of the epidermis. This makes the skin firm and impermeable to hydrophilic substances. One essential step during post-translational modification is the cross-linking of sulfhydryl groups within cysteine residues to disulfides. Sulfhydryloxidase (SOX) is an enzyme that is believed to catalyze disulfide bond formation and thereby promote the formation of the organism`s epidermis. The idea that SOX is involved in the keratinization process is so far based on results that have been obtained in studies on neonatal or adult animals. This work focusses on the foetal epidermis and demonstrates where and when the enzyme is first detectable in the prenatal epidermis. For this purpose, skin of prenatal rat at different days of gestational stage and newborn rat was treated with immunohistological and immunofluorescent techniques. SOX was detected at the same time as the first histological signs of keratinization became visible in the uppermost layers of the epidermis. Furthermore SOX was detected specifically in the stratum granulosum of newborn rats. Moreover, rat esophagus was also examined as another example of keratinizing epithelium using the same methods as described above. SOX was detected at the same time with the beginning of keratinization in the cell layers where the cornification process takes place. The reaction catalyzed bei SOX produces H2O2 which is believed to be degraded by catalase (CAT). Thus in this work we study when and where both SOX and CAT are observed during the epidermal differenziation of rat skin. CAT appears in the same cell layers as SOX, but shows a temporal delay of one day. We show - for the first time - that both SOX and CAT are correlatet with the keratinization process starting at day 18 of gestation. Together these results strongly support the hypothesis that SOX plays a key role within the keratinization process and that CAT is involved in the degradation process of the accruing H2O2.