[Experimental investigations on the regeneration of aortic endothelial cells. Automatic and visual evaluation of autoradiograms (author's transl)].

Autoradiographic studies on plane preparations using 3H-thymidine and pulse cytophotometric investigations on scrape preparations of aortic endothelium from 34 rabbits have brought the following results: By means of multiple 3H-thymidine-injections the number of labelled endothelial cells is higher in young growing animals than in older rabbits; pulse cytophotometrically we did not find any indication of polyploidization processes; from that we conclude a decrease of the growth fraction with advancing age. In comparison to visual counting the automatic image analysis is a highly effective method for the evaluation of autoradiograms. After multiple 3H-thymidine applications the mean blacking intensity of the labelled cell nuclei is lower in 2 months old animals than in 12 months old rabbits; that may mean an increase in the S-phase duration of the proliferating endothelial cells of the older animals. In the area with branching sites there are more 3H-thymidine-labelled endothelial cells than in the neighbouring vascular segments. The significance of these findings for the preferential incidence of arteriosclerosis in this area is discussed.