On the biochemical mechanism of tumorigenesis in mouse skin. VII. The effects of tumor promoters on 3H-choline and 3H-glycerol incorporation into mouse epidermal phosphatidylcholine in relation to their effects on 3H-thymidine incorporation into DNA.

The kinetics of the stimulation of phospholipid and DNA biosynthesis in mouse epidermis after treatment with various tumor promoting agents has been investigated. 3H-choline and 3H-glycerol were used as precursors for phosphatidylcholine. An early stimulation of 3H-choline incorporation into phosphatidylcholine is observed which always precedes the stimulation of 3H-thymidine incorporation into epidermal DNA. This is interpreted as being a manifestation of the proliferation of cellular membranes in preparation for cell division. Appreciable differences are observed in the incorporation of 3H-choline and 3H-glycerol into phosphatidylcholine, the possible reasons for which are discussed. It is concluded that 3H-choline incorporation is a more reliable parameter for the measurement of phosphatidylcholine biosynthesis than 3H-glycerol incorporation. The relationship between those effects on phospholipid synthesis and the tumor promoting activity of the substances tested is discussed.