STUDIES WITH 17-BETA(16-ALPHA-[125I]IODO)-ESTRADIOL, AN ESTROGEN RECEPTOR-BINDING RADIOPHARMACEUTICAL, IN RATS BEARING MAMMARY-TUMORS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 22  (5) , 459-464
Abstract
The distribution of 17.beta.(16.alpha.-[125I]iodo)-estradiol (I-E2) was studied in tumor-bearing and normal rats. High early adrenal-to-blood ratios (up to 22 at 5 min) were seen in all groups but this fell to 6 at 1 h. Uterus-to-blood ratios of 15 were found and these were fairly constant up to 2 h after administration. Uptake of label in the uterus, but not in the adrenals, was sensitive to excess diethylstilbestrol, which competes with I-E2 for estrogen receptors. Mean tumor-to-blood ratios of 1.4, 5.5 and 8.7 were seen at 1 h in rats with transplanted, spontaneous and N-nitrosomethylurea-induced tumors, respectively. Diethylstilbestrol reduced uptake of label by spontaneous tumors. Most of the radioactivity was excreted in the bile by 1 h. Better estrogen-receptor-binding radiopharmaceuticals can probably be designed.