UPTAKE OF RADIOACTIVE OESTRADIOL IN SOME ORGANS OF IMMATURE MICE.

ABSTRACT The uptake of radioactivity in some organs after the injection of oestradiol-3H to immature mice has been studied. The uterus and vagina contained more radioactivity per unit wet weight than skeletal muscle, for at least 15 hours. The uptake in the uterus and vagina could be inhibited by carrier oestradiol at a dose level of about 0.3 μg. Oestradiol accumulated by the uterus and vagina could not be easily displaced by a second injection of oestradiol. Oestrogen-stimulated uteri and vaginae retained their capacity to take up oestradiol. The structure specificity of the uptake was demonstrated by the two 17-OH isomers of oestradiol. 17β-oestradiol was more uterotrophic than the 17α-isomer and the 17β-isomer was also a stronger inhibitor of 17β-oestradiol-3H uptake in uterus and vagina than the 17α-isomer. This indicates a relationship between uptake in the target organs and oestrogenic activity. Progesterone and cortisol given before oestradiol-3H did not depress the uptake of radioactivity. Testosterone if anything stimulated the uptake. The uptake in liver and muscle was essentially not inhibited.