Estrogen receptor binding radiopharmaceuticals: II. Tissue distribution of 17 alpha-methylestradiol in normal and tumor-bearing rats

• Published in: The Journal of nuclear medicine (1978) Vol. 24; no. 6; p. 522
• Main Authors: Feenstra, A, Vaalburg, W, Nolten, G M, Reiffers, S, Talma, A G, Wiegman, T, van der Molen, H D, Woldring, M G
• Format: Journal Article
• Language: English
• Published: United States 01.06.1983
• Subjects: 9,10-Dimethyl-1,2-benzanthracene; Animals; Estradiol - analogs & derivatives; Estradiol - metabolism; Female; Mammary Neoplasms, Experimental - chemically induced; Mammary Neoplasms, Experimental - metabolism; Rats; Rats, Inbred Strains; Receptors, Estrogen - metabolism; Tissue Distribution; Uterus - metabolism
• ISSN: 0161-5505

Tritiated 17 alpha-methylestradiol was synthesized to investigate the potential of the carbon-11-labeled analog as an estrogen-receptor-binding radiopharmaceutical. In vitro, 17 alpha-methylestradiol is bound with high affinity to the cytoplasmic estrogen receptor from rabbit uterus (Kd = 1.96 x 10(-10)M), and it sediments as an 8S hormone-receptor complex in sucrose gradients. The compound shows specific uptake in the uterus of the adult rat, within 1 hr after injection. After 30 min the uterine uptake was 1.73% dose/g. In female rats bearing DMBA-induced tumors, specific uterine and tumor uptakes were observed, although at 30 min the tumor uptake was only 23-30% of the uptake in the uterus. Tritiated 17 alpha-methylestradiol with a specific activity of 6 Ci/mmole showed a similar tissue distribution. Our results indicate that 17 alpha-methylestradiol is promising as an estrogen-receptor-binding radiopharmaceutical.