The Incorporation of Tritiated Uridine in Hair Germ and Dermal Papilla During Dormancy (Telogen) and Activation (Early Anagen)

During dormancy there is very little incorporation of [3H]uridine in cells of hair germ and dermal papilla. During activation (both spontaneous and experimental) there is a marked increase in this parameter, expecially in the cells of the germ. After experimental activation by plucking, the increase in label in the germ is evident by 6 hr, reaching an initial maximum by 24 hr. The initial increase in [3H]uridine incorporation after activation precedes the increase in [3H]thymidine incorporation found previously, by about 6 hr. No evidence was found that the increase in [3H]uridine of papilla cells precedes the increase in [3H]uridine of germ cells. This finding militates against the possibility that the dermal papilla is triggered into an inductive role (vis-á-vis the germ cells) by means of circulating steroid hormones.