Long-term effects of gamma-irradiation on cultured human thyroid cells.

When differentiated 15-day-old cultures of human thyroid glands were irradiated they exhibited a high degree of radiosensitivity, an absence of split-dose recovery, an increase in the number of non-senescent colonies observed over four passages, increased focus formation on the confluent postirradiation monolayer and a shift in the isozyme pattern of LDH towards the anaerobic form (LD 5). The effects are similar to those previously observed for irradiated sheep thyroid cultures, but occurred at lower radiation doses.