Dibutyryl cyclic AMP-induced differentiation of epidermal cells in tissue culture

Histochemical and biochemical techniques have been used to compare the effects of dibutyryl cyclic AMP on epidermal cells and dermal cells in primary tissue culture. Rhodamin B staining showed only scattered positive cells in nontreated epidermal cells and a few contaminating keratinizing cell foci in both nontreated and treated dermal cell cultures. In contrast, treated epidermal cells stained strongly and had many keratinizing cell foci. A significant increase in histidine, cystine, and arginine incorporation was noted in epidermal cells treated with dibutyryl cyclic AMP as compared to untreated epidermal cells and to dermal cell cultures both treated and untreated. Dibutyryl cyclic AMP had no significant effect on leucine and phenylalanine incorporation. These results seem to suggest that the intracellular level of cyclic AMP not only controls the synthesis of DNA by epidermal cells in culture but also induces the process of differentiation toward keratinization.