An autoradiographic study of cell kinetics in epidermis of the toad Bufo bufo bufo (L)

Under normal conditions, the toad Bufo bufo bufo molts about once a week. It was considered of interest to study whether the rhythmic pattern of cell loss through shedding of a stratum corneum is correlated with a rhythmic production of cells in stratum germinativum. An autoradiographic investigation of cell kinetics in toad skin using [3H]-thymidine and [14C]-thymidine as precursors revealed that cell production in stratum germinativum is a continuous process, and the cell production rate is much higher than is required for replacement of the cells lost with each molt. The parameters measured, i.e., % labeled cells, length of cell cycle, and S-phase, as well as migration of labeled cells from stratum germinativum toward stratum corneum support the assumption of an inhomogeneous cell population in stratum germinativum. A model proposed by Potten form the cellular organization of mouse epithelium provides a useful basis for the interpretation of the results obtained in the present study.