Life and Medical Sciences
Cell & Developmental Biology
Wiley InterScience Backfile Collection 1832-2000
Epidermal G1-chalone and transforming growth factor-β (TGFβ), two endogenous inhibitors of epidermal cell proliferation, were compared with regard to several effects on epidermis in vivo and in vitro. Both factors inhibited DNA labeling in a rat tongue epithelial cell line, with similar kinetics and half-maximal effects at approximately 1 pg/ml (enriched chalone) and 1 ng/ml (TGFβ). For primary neonatal mouse keratinocytes, (TGFβ) was found to be a rather strong inhibitor of cell proliferation, whereas chalone showed only a weak effect on cells grown in medium containing 1.2 mM Ca2+ and no effect at all in the presence of 0.06 mM Ca2+. Vice versa, upon i.p. injection, only chalone was able to inhibit mouse epidermal DNA synthesis in vivo, whereas TGFβ had no effect at all. A moderate increase of transglutaminase activity in neonatal primary mouse keratinocytes was induced by both factors at concentrations of about 300 pg TGFβ/ml and 10 pg chalone fraction/ml. Chalone did not compete with TGFβ for specific binding sites on primary murine keratinocytes. A polyclonal "chalone antiserum" did not interact with TGFβ, and a neutralizing TGFβ antibody that inhibited the effect of TGFβ on cell proliferation could not block the inhibitory effect of chalone on RTE2 cells. In contrast to TGFβ, epidermal G1-chalone did not induce proliferation of NIH-3T3 cells. These results indicate that epidermal G1-chalone and TGFβ are two different inhibitors of epidermal cell proliferation.
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