NUMERICAL VARIATION OF DARK CELLS IN NORMAL AND CHEMICALLY-INDUCED HYPERPLASTIC EPIDERMIS WITH AGE OF ANIMAL AND EFFICIENCY OF TUMOR PROMOTER

  • 1 January 1981
    • journal article
    • research article
    • Vol. 41  (11) , 4437-4440
Abstract
The percentage of dark basal keratinocytes was quantitatively assessed in normal epidermis of Sencar mice before and after birth and in adult epidermis after topical application of several compounds of varying promoting efficiency. The percentage of dark keratinocytes reached a maximum at the 19th day of gestation (.apprx. 40%) and fell abruptly after birth (.apprx. 3%). Old animals exhibited a very low number of dark basal cells (0.2%). After topical application of the weak promoters resiniferotoxin, anthralin, ethylphenylpropiolate and 12-deoxyphorbol-13-2,4,6-decatrienoate, the percentage of dark cells in young adult epidermis did not differ markedly from that in control (acetone-treated) specimens. The strong 1st-stage promoters 4-O-methyl-12-O-tetradecanoylphorbol-13-acetate and calcium ionophore A 23187 and the strong complete promoter 12-deoxyphorbol-13-deoxyphorbol-13-decanoate induced the appearance of large numbers of dark keratinocytes in a percentage similar to that seen after 12-O-tetradecanoylphorbol-13-acetate application (.apprx. 20%). The similarities between the dark keratinocytes seen after topical application of 12-O-tetradecanoylphorbol-13-acetate or other strong promoters and the dark cells observed in the fetal epidermis before the onset of the adult type of epidermal keratinization indicate that potent and/or 1st stage tumor promoters can be identified by their ability to induce cells resembling fetal-type dedifferentiated keratinocytes.