The water content in the epidermis of mice undergoing carcinogenesis by methylcholanthrene.

Studies on the role of the minerals in epidermal carcinogenesis of mice induced by methylcholanthrene have been described (2), and the need for the determination of the water content of the epidermis became obvious in investigations on the succinic dehydrogenase and cytochrome oxidase activities of the epidermis (3). Since the latter are expressed as cu. mm. of oxygen consumed per mgm. dry weight of tissue per hour, it became imperative to ascertain in what way the water content behaved during carcinogenesis so that the activities of the enzymes could be placed on a more adequate basis of reference. In our previous studies the epidermis was separated from the dermis at 50 ~ C., and no attempt was made to determine the water content since one would expect some loss of water at this temperature. We have overcome this obstacle through separating epidermis from the dermis at room temperature by the following procedure: A block of wood was covered with a sheet of plastic and the whole mouse skin, fur side up, was stretched tightly over it with pins. With a small dull scalpel the epidermis was scraped off the dermis. Histological examination of the dermis revealed that it was not disturbed, although a few epidermal cells were left in contact with it. Fig. 1 shows the procedure for the separation process. The water content of normal, untreated epidermis was determined by drying the sample to constant weight at 105 ~ C., and also by the Bidwell-Sterling toluene extraction method. With the former procedure the epidermis upon removal from the dermis was placed into a small, round-bottom, stoppered-flask, which was submerged in a mixture of ice and water to minimize loss of water by evaporation. The sample was then weighed and dried to constant weight at 105 ~ C. A micro Bidwdl-Sterling apparatus was constructed with Pyrex glass and the receiving vessel was calibrated with mercury. The samples of epidermis