Abstract
The action of estrogens on target organs has been amply reviewed (1-3). Since the report by Jensen and Jacobson (4), demonstrating accumulation and retention of estradiol in rat uterine tissue, many investigators have turned to the use of tritiated estradiol with high specific activity as a tool for studying mechanisms of estrogen action. The effect of estrogen pretreatment on the uptake of radioactive estradiol has been studied in several laboratories with variable results (4-8). This report defines the conditions under which various estrogens stimulate the uptake of tracer estradiol by the mouse uterus.
Materials and Methods. Five to ten female Cox mice weighing 11-13 g were used per group. At sacrifice, the uteri were quickly removed, dissected free of extraneous tissue, and weighed after uniform blotting to remove excess fluid. The uteri were transferred directly to counting vials and dissolved in 1.0 ml NCS Reagent (Nuclear Chicago) with gentle warming. Diatol was added and radio-activity was determined by liquid scintillation spectrometry. Disintegrations per minute were determined by using an internal standard.
Estradiol-6,7 3H (42.5 Ci/mM) was obtained from New England Nuclear. Tracer injection solutions were prepared in 5% ethanol-saline and contained 1 μCi/0.1 ml (6.4 ng estradiol/μCi). In all cases the tracer dose of 1 μCi estradiol was given exactly 1 hr prior to sacrifice. Priming doses of estrogen were prepared in corn oil or saline, and the concentration was adjusted so that the injection volume was 0.1 ml.
Results.When 0.03 μg estradiol-17β was given subcutaneously in corn oil or intravenously in saline at various times up to 6 hr prior to sacrifice, the uptake oftracer estrogen was increased at 3 hr after priming with no furher increase at 6 hr (Fig. 1). The response developed somewhat faster with intravenous injection, but the magnitude was not so great.
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