[Transition of oxic cells to hypoxic cells in a murine squamous cell carcinoma]

(125I) Iododeoxyuridine labeling of a squamous cell carcinoma and follow-up of 125I activity at the tumor in situ revealed that the 125I activity remained at a constant level from the 24th to the 100th hour post-labeling and then decreased with a half time of about 200 hr. Autoradiographic studies with (3H) thymidine showed that the tumor cells were labeled around capillaries, spread through the corded structure (the cord) and finally reached the necrotic regions. One could speculate that the constant 125I period represents the transit time of the labeled cells through the cord and that the decline occurs mostly in the necrotic regions.