Walker 256 carcinosarcoma cells were labeled in vivo in animals with use of a single dose of tritiated cytidine (CR-5-3H). Heavily labeled tumor cells were then given intravenously to new recipient animals. These recipients were killed at different time intervals and the lung tissue was prepared for histologic study and autoradiography. Labeled tumor cells were readily seen in the alveolar capillaries of the recipients' lungs as early as one minute after the intravenous injection with very little variation in the grain count. At 12 hours there was a considerable dispersion of the grains. Dispersion was more prominent at 24 hours. Tumor cells were seen penetrating the vessel walls into alveolar air spaces within one hour. Tumor cell loss through such local destruction and physical exit from the circulation is seen as a partial explanation for the low fraction of metastatic takes of intravascular tumor cells.
Cliffton EE, Agostino D, Madden RE, Berechid JN. Distribution in the Lungs of Labeled Walker 256 Carcinosarcoma CellsAn Autoradiographic Study With Tritiated Cytidine. Arch Surg. 1971;103(3):373-375. doi:10.1001/archsurg.1971.01350090055012