tretinoin and n-hexadecane

The rate of cell proliferation in the basal cell layer by epidermal hyperplasia of guinea pig ear was investigated with cytofluorometric method. Epidermal hyperplasia was caused by tape stripping or the application of n-hexadecane or retinoic acid. In non-treated epidermis, the mean of the relative numbers of cell in each phase to the total cell number was 62.8% (G1), 34.6% (S) and 2.6% (G2 + M), respectively. In the case of tape stripping, growth in the relative number of S phase cells showed approximately the same proportions at 3 to 12 h. At 24 h, the relative number of S phase cells was lower than that in non-treated epidermis. By the application of n-hexadecane, the relative number of S phase cells was highest at 6 h. It was highest at 3 h by the retinoic acid application. On the other hand, the value of nuclear protein in G1 cells was highest at 6 h by both tape stripping and n-hexadecane application, while the value by retinoic acid was similar to that in non-treated epidermis.

Topics: Alkanes; Animals; Cell Division; Cell Nucleus; DNA; Epidermis; Flow Cytometry; Guinea Pigs; Hyperplasia; Male; Tretinoin

Ear skin of adult mice was used as a source of explant cultures of epidermal cells and the requirements for growth were defined. Two growth phases were observed, the first more rapid than the second. All-trans-retinoic acid or n-hexadecane was applied topically for up to 9 days and the skin was then used for explant cultures. During both treatments the ear became red and swollen. The epidermis became hyperkeratotic or deprived of its horny layer. The thickness of the stratum Malpighii increased to up to nine layers, from the normal of two or three layers. The stratum granulosum became multilayered and keratohyalin granules were abundant. Explants of n-hexadecane-treated skin behaved exactly as their normal controls. All-trans-retinoic acid included an increase in migratory cell activity during the first growth phase. In the second growth phase the growth rate was similar or lower than that of the controls.

Topics: Alkanes; Animals; Cell Division; Cell Movement; Culture Techniques; Epidermal Cells; Epidermis; Mice; Tretinoin