OESTROGEN BINDING IN THE MOUSE UTERUS

Abstract

Tissue slices from immature mice were incubated at 37[degree] C in a buffer with tritium-labelled estrogens, rhe target tissues, uterus and vagina are found to take up much more 17[beta]-estradiol than several non-target tissues (the diaphragm, heart, thymus, spleen, stomach or kidney). In addition, when tissue slices, which have been preloaded with 17[beta]-estradiol, are washed, the uterus and vagina retain the estrogen much more strongly than the non-target tissues. Uteri preloaded in vivo with 17[beta]-estradiol also retain the accumulated estrogen strongly on washing in vitro. The synthetic estrogen meso-hexestrol is also selectively taken up and retained by the uterus but to a lower extent than 17[beta]-estradiol. The isomeric racemic hexestrol is a much less potent oestrogen a id is not selectively bound by the uterus. However, the retention of racemic hexestrol both by the uterus and the diaphragm is high. The preferential uterine uptake of the potent estrogens is inhibited by low Incubation temperature. A low incubation temperature also inhibits the wash-out of estrogens from the uterus. There was no evidence of extensive metabolic transformations of the estrogens investigated. It is likely that the mode of estrogen retention in the mouse uterus and vagina is due to non-covalent binding.