Anomalies in Chromosomes of the Circulating Leukocytes in Man Following Large Doses of Radioactive Iodine1

Abstract

Quantitative measurements of DNA in nuclei of I^l3l-irradiated thyroids have demonstrated some values somewhat less than the normal; when a stimulus (thiouracil) for cell division is superimposed, many values greater than twice the normal result. These observations imply nuclear damage or alteration in the irradiated cells. Techniques now available make it possible to visualize clearly the individual chromosomes of human cells. One of these techniques was used to investigate the chromosomes of circulating leukocytes following I¹³¹ administration. This report concerns many observations on a single patient who had thyroidal carcinoma with functioning metastases and who was given a therapeutic dose of 167 me of I¹³¹. At frequent intervals during the first 24 hr, and less frequently thereafter for 14 days, the concentration of radioactivity and the leukocyte and differential counts were determined. Simultaneously, cultures of leukocytes were made as a source of chromosomal preparations. Spreads of chromosomes from many individual cells of each culture were counted and analyzed. Numerous anomalies of structure and number were found. In most instances the abnormality was a chromosomal number less than the normal of 46, but in some instances the counts exceeded the normal. An occasional 4n nucleus was seen. Chromosomal breakage and dicentric forms occurred. The maximal frequency of anomalies occurred during the period of 3–12 hr after I¹³¹ administration and corresponded to the maximal concentration of I¹³¹ in the blood.