The Survival of Thyroid Cells: In Vivo Irradiation and in Situ Repair

Abstract

The survival of rat thyroid cells irradiated in vivo and removed immediately for transplantation survival assay was compared with thyroid cells irradiated in vitro and thyroid cells irradiated and left in situ for 24 h before transplantation survival assay. The Do [median lethal dose] for thyroid cells irradiated in vivo and removed immediately for assay was 195 rad; N [extrapolation number] was 4 and Dq [quasi-threshold dose] is 270 rad. These parameters were not significantly different from values when thyroid cells are irradiated in vitro. These parameters were compared to those of thyroid cells irradiated and left in situ for 24 h. The latter had a greater N and Dq, but there was no significant difference in Do. The form of repair of potentially lethal damage apparently is dependent on the tissue environment (in situ repair) as described for irradiated rat mammary gland cells.