Cellular proliferation kinetics of the murine sarcoma induced by the Moloney sarcoma virus

Cell proliferation kinetics of the sarcoma induced by Moloney virus was studied in newborn Swiss OF1 mice. After in vivo injection of tritiated thymidine, followed by autoradiography, it was shown that the majority of cells were actively proliferating (labelling index; 31%, growth fraction 78%). The mean cell cycle was 16 hr and cell loss was relatively low (cell loss factor 48%). The study of tumour specific activity with time after a single [in vivo] injection of [3H]dR or [125I]UdR did not demonstrate the same degree of cell loss as that calculated by autoradiography. This result is consistent with a massive reutilization of radioactivity released by normal tissues.