Epidermal cell population kinetics after repeated applications of some hyperplasia-producing substances

Abstract

The initial and the long term effects of repeated surface applications to the skin of hairless mice (hr/hr) of benzene, cantharidin in benzene, and 20-methylcholanthrene, respectively, have been examined. The growth parameters have been evaluated by means of the Colcemid method. The reactions of the epidermal cell population have been interpreted from cybernetic point of view and as biological phenomena. Both benzene and cantharidin provoked alterations in the dynamics of the epidermal cell population that can readily be explained in terms of cybernetics. The initial reaction after application of methylcholanthrene was also in conformity with this concept, but later on after treatment with this agent a striking prolongation of the mitotic duration was observed in spite of the fact that the mitotic rate was increased too. These findings were difficult to reconcile with the simple cybernetic system. Other mechanisms must be discovered. Some possible explanations are discussed.