Cycling S-phase cells in animal and spontaneous tumours. I. Comparison of the BrdUrd and 3H-thymidine techniques and flow cytometry for the estimation of S-phase frequency.

Evaluation of the proliferative activities of cell populations has mainly been restricted to the use of autoradiography and flow cytometric measurements. The introduction of a new BrdUrd specific antibody makes it possible to determine exactly the DNA synthesizing cells. The BrdUrd technique is safe with respect to handling and the results are obtained within five hours. The suitability of the BrdUrd labelling procedure has been studied in different cell lines and compared with 3H-thymidine autoradiography and flow cytometry.