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Tissue distribution of 2- and 4-[203Hg]-estradiol in mammary-tumor-bearing rats
Abstract:
The newly synthesized 2-[203Hg]-estradiol-17 beta and 4-[203Hg]-estradiol-17 beta were injected into Fischer female rats bearing transplanted mammary adenocarcinomas and into Sprague-Dawley female rats bearing spontaneous mammary tumors. Four days after injection, tumor to blood ratios (and uterine to blood ratios) in the various groups were between 5 and 14, compared to a ratio of unity observed in normal mammary glands. When injected into male rats, the accumulation of 4-[203Hg]-estradiol in the prostate and in the epididimis was very low. With minute doses of 4-[203Hg]-estradiol injected into healthy male rats, the whole-body retention of the drug was found to decrease exponentially with time, and biphasic first order kinetics were observed. With pharmacological doses of the same drug, the clearance exhibited a biphasic pattern.
Insights
Newly synthesized mercury-203 labeled estradiol ([203Hg]-estradiol) showed significant tumor accumulation in rats with mammary tumors. This radiolabeled compound demonstrated potential for tumor imaging and diagnostic applications.
Area of Science:
- Radiochemistry
- Oncology
- Pharmacokinetics
Background:
- Mammary tumors often exhibit altered estrogen receptor expression.
- Developing targeted radiopharmaceuticals for cancer imaging is crucial.
Purpose of the Study:
- To synthesize and evaluate mercury-203 labeled estradiol ([203Hg]-estradiol) analogs for potential use in imaging mammary tumors.
- To assess the biodistribution and pharmacokinetic profile of [203Hg]-estradiol in tumor-bearing and healthy rats.
Main Methods:
- Synthesis of 2-[203Hg]-estradiol-17 beta and 4-[203Hg]-estradiol-17 beta.
- Injection of radiolabeled compounds into female rats with transplanted or spontaneous mammary tumors, and into male rats.
- Measurement of tissue-to-blood ratios (tumor, uterus, prostate, epididymis) at specific time points post-injection.
- Analysis of whole-body retention and drug clearance kinetics in male rats using minute and pharmacological doses.
Main Results:
- Tumor-to-blood ratios ranged from 5 to 14 in tumor-bearing rats four days post-injection, significantly higher than the ratio of unity in normal mammary glands.
- Uterine-to-blood ratios were also elevated.
- Low accumulation of 4-[203Hg]-estradiol was observed in the prostate and epididymis of male rats.
- Whole-body retention in male rats decreased exponentially with time, showing biphasic first-order kinetics for minute doses and a biphasic clearance pattern for pharmacological doses.
Conclusions:
- [203Hg]-estradiol analogs demonstrate selective uptake in mammary tumors, suggesting their potential as diagnostic imaging agents.
- The biodistribution profile indicates favorable tumor targeting with relatively low uptake in non-target organs like the prostate.
- Pharmacokinetic studies reveal distinct elimination patterns depending on the administered dose, providing insights for potential therapeutic applications.