Increased uptake of iodide by hormone-responsive compared to hormone-independent mammary tumors in GR mice.

The uptake of 125-iodide by transplanted hormone-responsive (HR) or hormone-independent (HI) mammary tumors, normal mammary tissue and skeletal muscle was compared in GR mice. The uptake of 125-iodide by HR mammary tumors in mice treated with progesterone and oestrone (P+O) was about 20 times greater than the uptake of 125-iodide by HI mammary tumors in mice not treated with P+O. This difference in uptake of 125-iodide by HR and HI mammary tumors could not be attributed to the difference in the hormonal status of the mice since uptake of 125-iodide was also low in HI tumors in mice receiving P+O treatment. The uptake of 125-iodide by HR mammary tumors was greatly reduced by the simultaneous injection of either an excess of non-radioactive iodide or of perchlorate. Uptake of 125-iodide by normal mammary tissue and skeletal muscle was similar was similar in all groups of tumor bearing mice, and was not influenced by the presence of an excess of non-radioactive iodide or of perchlorate. The possible clinical significance of these findings is discussed.