Tissue distribution of 2- and 4-[²⁰³Hg]-estradiol in mammary-tumor-bearing rats

The newly synthesized 2-[²⁰³ Hg]-estradiol-17β and 4-[²⁰³Hg]-estradiol-17β 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.