Homeostatic regulation of epidermal cells in culture.

The growth potential (DNA synthesis) of purified epidermal basal cells in culture, according to time reveals two peaks, at days 1 and 6. The same potential estimated in total cultures of epidermal cells (including basal and high level cells) shows only one peak at day 9. This suggests that hig-level mature cells inhibit DNA synthesis in basal cells in culture. This interpretation has been confirmed in showing that increasing amounts of mature cells inhibited DNA synthesis in basal cells in a dose dependent manner. Basal cells in culture are therefore susceptible to homeostatic regulation. However, this regulation is not tissue specific since DNA synthesis was also inhibited by mature epidermal cells in cultures of dermal as well as bone marrow cells. Assuming that the culture of epidermal cells is representative of the in vivo situation, these experiments would suggest that the specificity of action of the G1 chalone in vivo might depend as much on the target tissue as the proper nature of the inhibitor.