An autoradiographical topological study of the epithelial cell proliferative activity in the ascending colon of the mouse using a modified technique for determining the fraction of labelled mitoses (FLM).

In a previous study of the mouse ascending colon we showed that epithelial cell proliferation is more active on the tops of mucosal folds than in the flat mucosal areas between folds. In order to define the cytokinetic characteristics of this phenomenon more precisely, we have undertaken an autoradiographic investigation with 3H-thymidine. The fraction of labelled mitoses (FLM) curves and cell labelling indices have been worked out in fold top areas (FTA) and on flat areas off the folds (OFA). A new method has been adopted to draw the FLM curves. The results show no difference between the cell cycle times or in the times corresponding to G2-phase and S-phase in FTA and OFA. In contrast, the proliferative cell compartment in FTA is 40% higher than in OFA.