E-17-ALPHA-[I-125]IODOVINYLESTRADIOL - AN ESTROGEN-RECEPTOR-SEEKING RADIOPHARMACEUTICAL

Abstract

Through the use of radioiododestannylation, the specifically labeled E-17.alpha.-[125I]iodovinylestradiol [(125I)VE2] was synthesized rapidly and in high yield from the stable precursor E-17.alpha.-tributylstannylvinylestradiol (SnVE2), and its biodistribution was determined in immature female rats. The agent accumulated in the uterus, achieving a peak uptake of 0.465% ID[initial dose]-kg/g at 2 h. Uterus-to-blood ratios of 19 and 16 occurred at 1 and 2, respectively, declining to 7 by 4 h after injection. The uptake of (125I)VE2 by the uterus at 2 h was reduced 58-65% by pretreatment of the immature rats with estradiol (5 .mu.g) or tamoxifen (100 .mu.g), and compared with 16.alpha.-[125I]iodoestradiol, (125I)VE2 showed greater uterine uptake and similar uterus-to-blood ratios. The ease of preparation of the radioligand represents an advantage over the synthetic procedures for other estrogen-receptor-seeking agents [used in breast tumor diagnosis].