Autoradiographic studies on the mode of growth in jejunal crypt cells of the mouse

SUMMARY Cell kinetic parameters of the jejunal crypt epithelia of the mouse were reinvestigated to determine if a steady state system with constant frequency distribution of cells throughout the cycle exists and if all cells which are labelled after an injection of 3 H‐thymidine subsequently divide. 3 H‐ and 14 C‐thymidine double labelling experiments indicated that the cell flux into and out of S‐phase is equal and are a direct experimental proof of the existence of a steady state. A generation time of 14 h was obtained by a 3 H‐ and 14 C‐thymidine double labelling modification of the percent labelled mitoses method and a proliferative pool size of 75% determined. Evidence is presented that synthesis of metabolic DNA does not occur in the crypt.