EFFECT OF APHIDICOLIN ON DNA-SYNTHESIS IN CULTURED HUMAN THYROID-CELLS

To investigate whether partial inhibition of DNA synthesis affects the growth of thyroid cells, human thyroid cells were cultured in the pre sence of aphidicolin for 24 h. After removal of aphidicolin, the growt h of thyroid cells was evaluated by [H-3] thymidine uptake and analysi s of cell cycle by flow cytometry. In Graves' thyroid cells, [H-3] thy midine uptake and the percentage of cells in S+G(2)/M phase increased during 24 hours after washout of aphidicolin, whereas those were not a ugmented in normal thyroid cells. Thus, the acceleration of DNA synthe sis occurred after the partial inhibition of it by aphidicolin in Grav es' thyroid cells, but not in the normal thyroid cells. This phenomeno n might, at least in part, explain the difference of growth regulation between Graves' and normal thyroid cells.