Cytophotometric manifestation of the biochemical changes in various skin constituents induced by a single subcutaneous administration of 7,12-dimethylbenz(a)anthracene in rabbit.

ABSTRACT

The effect of a single subcutaneous administration of 7,12-dimethylbenz( a)anthracene, the powerful complete carcinogen, under the skin was studied in the rabbit. The study reports an ordered sequential biochemical and cytophotometric changes induced by the carcinogen. While the biochemical studies comprised of sequential quantitative estimations of DNA, RNA and protein per mg of skin, the cytophotometric studies consisted of the estimation of the level of macromolecules in a cell/nucleus, in different skin constituents viz. epidermis, hair follicle shaft region and hair follicle bulb region. Biochemical results indicate an initial rise in the level of DNA and RNA and reduction in protein upto 20 days. From 40 to 60 days treatment duration there was a ‘steady-state’ showing a constant level of all the parameters while the highest peak was observed on the 80th day. The site of these biochemical changes among different skin constituents was determined with the help of cytophotometer which indicates the highest level of nucleic acids in epidermis region right from the initial stage (i.e. 10th day) to the 90th day of treatment in comparison to two other regions hair follicle shaft and hair follicle bulb regions. Histological studies, on the other hand, reveal a greatly, though gradual, increased nuclear area and the highest rate of proliferation only in hair follicle bulb region, thus suggesting a definite role of this region of the skin in the carcinogenesis. All these results suggest that the important event in the initiation phase of 7,12-dimethylbenz( a)anthracene mediated skin carcinogenesis in rabbit might be associated with epidermal region but the role of hair follicle bulb region should also be considered as of an equal significance during the process. A conspicuous difference in the behaviour of rabbit skin constituents has been noted when the results of the study are compared with the earlier reports on mice.