title: Distribution of catalase and its modulation by 12-O-tetradecanoylphorbol-13-acetate in murine dermis and subpopulations of keratinocytes differing in their stages of differentiation.
abstract: Topical treatment of female SENCAR mice with 12-O-tetradecanoylphorbol-13-acetate (TPA) reduced both dermal and epidermal catalase-specific activities 38% and 51% within 6 h and 18 h of promoter application, respectively. Dermal catalase activity recovered to control levels within 72 h of treatment whereas epidermal catalase activity remained suppressed. Activity measurements were also made in four subpopulations of keratinocytes prepared by Percoll gradient centrifugation that differed in their stages of differentiation. Catalase-specific activity increased with keratinocyte maturity and ranged from 45-54 U/mg protein for basal cell preparations to 252 U/mg protein for granular-squamous cell preparations. Pretreatment of the epidermis for 16-18 h with TPA (2 micrograms) uniformly reduced catalase-specific activity 46-52% in all keratinocyte subpopulations prepared by Percoll gradient centrifugation. Similarly, plots of catalase units per cell versus extracted protein per cell suggested 55-60% decreases in catalase activity in basal and spinous cell keratinocytes of TPA treated epidermis. Furthermore, catalase-specific activity in homogenates of whole epidermis (144-182 units/mg protein) was most similar to the activity of the granular/squamous keratinocyte subpopulation. Collectively, these studies suggest that: (i) TPA reduces the capacity for H2O2 detoxification by catalase throughout the epidermis; and (ii) activity measurements on unfractionated epidermal preparations may not be representative of the basal cell keratinocyte population.
authors: University of Texas System Cancer Center, Science Park, Research Division, Smithville 78957.
authors: J J
authors: JJ
authors: Reiners
authors: M A
authors: MA
authors: Hale
authors: A R
authors: AR
authors: Cantu
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism*; D002454:Cell Differentiation; D002469:Cell Separation; D004789:Enzyme Activation / Q000187:drug effects; D004817:Epidermis / Q000201:enzymology; D000431:Ethanol / Q000494:pharmacology; D051379:Mice; D012867:Skin / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D000431:Ethanol; D002374:Catalase; D013755:Tetradecanoylphorbol Acetate