A system for the study of epidermal G1-chalone in cell culture. The rat tongue epithelial cell line RTE2

A pig-skin preparation enriched in epidermal G1-chalone when administered to cells of the rat tongue epithelial line RTE2 at concentrations of 3-300 micrograms/ml (dry mass) caused a 60% reduction in cell number. Three other cell lines showed essentially no growth inhibition during chalone treatment. The kinetics of chalone inhibition were similar to those observed in mouse epidermis in vivo. Five hours after the addition of chalone preparation in fresh medium a decrease in the rate of DNA synthesis was observed. Maximum inhibition at 12 h was followed by a subsequent increase in DNA synthesis, reaching control values again after 30 h. The inhibitory effect was dose-dependent up to 3 micrograms/ml. At higher concentrations the degree of inhibition remained constant at about 50% of the control up to 300 micrograms/ml. Removal of added chalone by changing the medium at the time of maximum inhibition gave rise to a complete recovery within 9 h. These results indicate a cell-line specific, non-toxic and reversible inhibitory effect of the chalone preparation which resembles that observed in the living animal. The RTE2 cell line may thus be considered to provide a highly sensitive experimental system suitable for more detailed studies on the mechanism of action of epidermal G1-chalone.