[I-125] 17-ALPHA-LODOVINYL 11-BETA-METHOXYESTRADIOL - INVIVO AND INVITRO PROPERTIES OF A HIGH-AFFINITY ESTROGEN-RECEPTOR RADIOPHARMACEUTICAL

  • 1 January 1984
    • journal article
    • research article
    • Vol. 25  (4) , 472-477
Abstract
17.alpha.[125I]Iodovinyl 11.beta.-methoxyestradiol ([I-125]MIVE2) was prepared with high specific activity (1500-2000 Ci/mmol) and a high affinity for the estrogen receptor (KA = 6.8 .times. 109 M-1) [rat uterus]. In vivo distribution studies using immature rats result in high levels of activity in the uterus (20-30% dose/g) with uterus-to-plasma ratios on the order of 68-100. Peak activity in the uterus is obtained between 2 and 4 h, and by 6 h 50% of the activity has washed out. The [I-125]MIVE2 exhibits a slower rate of washout relative to the washout of H-3 estradiol. By in vivo competition studies with nonradioactive estradiol, we found that 95% of the [I-125]MIVE2 bound in the uterus is specifically bound to estrogen receptors. The radioactive labeling of MIVE2 is sufficiently rapid so that [I-123]MIVE2 was synthesized and is currently in clinical trials [for dignosis of human breast cancer]. MIVE2 should be an excellent agent for the study of estrogen receptors in vivo and in vitro.