The Changes of Epidermal Lipid and Calcium in the Lesion of Skin Tumor and Non-tumor of Hairless Mice Induced by Vinyl Carbamate Epoxide and TPA
BACKGROUND: Chemically induced epidermal carcinogenesis is usually divided into two stages, the initiation and promotion. The initiation involves conversion of some epidermal cells into latent neoplastic cells and the promotion is proliferation of the transformed cells. Ethyl carbamate (EC) has been identified at low microgram quantities in various fermented beverages, distilled products and tobacco smoke. It has been known as a initiator of tumor. Oxidation of the ethyl group of EC is followed by dehydration to yield the carcinogen vinyl carbamate (VC). This is further oxidized to vinyl carbamate epoxide (VCO). VC and VCO proved to be much more carcinogenic than EC. OBJECT: This study is attemped to investigate the skin tumor and non-skin tumor in hairless mice induced by application of 12-0-tetradecanoyl-phorbol-13-acetate (TPA) on the skin initiated with VCO and its relationship with calcium gradient and epidermal lipid. METHODS: In this experiment, the tumor induction was performed by painting the mouse skin once a week for five weeks with VCO solution, and then 12-0-tetradecanoyl-phobol-13-acetate (TPA) was treated in the same manner twice a week for 40 weeks. We biopsied the skin at 5, 10, 25, 30, 35 and 40 weeks and stained the specimens with hematoxylin-eosin, Ru04 postfixation and ion capture cytochemistry for calcium staining. RESULTS: The results are summerized as follows 1. Cellular proliferation, hyperkeratosis and dysplasia of the epidermis were more prominent in skin tumors than non-skin tumors. Papillomas were developed at 8 weeks after application of VCO- TPA but not TPA alone. The occurrence of keratoacanthoma and squamous cell carcinoma was 33 and 39 weeks, respectively. 2. Calcium gradient was distorted in the only TPA treatment group but normal in the control group. Calcium deposition was increased through all layers of epidermis and the calcium gradient was disappeared in the epidermis of tumors in the VCO-TPA treatment group. These findings were similar to papilloma, keratoacanthoma and squamous cell carcinoma. 3. Fragmented, incomplete lipid bilayer formation, dilated intercellular spaces and multiple lacunar domains were prominent in the VCO-TPA and TPA treatment groups but not in the control group. The VCO-TPA treatment group has shown more epidermal lipid damage than that of the only TPA treatment group. 4. Diploid DNA histogram patterns were observed in all the control and TPA treatment groups. But aneuploidy was observed in 1 of 3 keratoacanthomas and 3 of 3 squamous cell carcinomas. CONCLUSION: From the above results, it is concluded that various skin tumors, such as papilloma, keratoacanthoma and squamous cell carcinoma or non-skin tumor were produced by VCO. Skin tumors showed various, distinctive light microscopic or electron microscopic changes compared to the non-skin tumor. It is thought that intercellular lipid change and calcium gradient disappearance in the epidermis have an important role in the carcinogenesis.
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