Stimulated mouse ear epidermis in explant culture- The effect of retinoic acid and hexadecane.

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.