Progesterone Receptor と Estrane系ステロイドとの相互作用

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  • The interaction of progestogens of the estrane series with progesterone receptor in rabbit uterine cytosol
  • Progesterone Receptor ト Estraneケイ ステロイド

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The purpose of this study is to determine the affinities and the binding radicals of progesterone receptor, and their effect on the formation of the progesterone-receptor complex which binds to chromatin.<BR>The uterine cytosol and the uterine chromatin were obtained from the estrogen primed immature female rabbit. 8S components were obtained after the 5-20% sucrose linear gradient centrifugation of uterine cytosol.<BR>1. A sedimentation profile of the progesterone binding macromolecule showed that 3H-progesterone formed 8S and 5S binding complex, and the 3H-progesterone-8S binding was effectively inhibited by norethindrone or ethynodiol diacetate, resulting in the relative increases of 3H-progesterone-5S binding and free progesterone.<BR>The effect of steroids on progesterone-8S binding was studied by a double reciprocal plot which showed that the following steroids were competitive inhibitors for progesterone 8S binding, and the order of the affinity for progesterone receptor was norethindrone (Ki=2.3×10-9M) >5α-dihydronorethindrone (Ki=6.0×10-9 M) > norethindrone acetate (Ki=8.8×10-9M) > lynestrenol (Ki=9.7×10-9M) >17α-ethynyl-4-estren-3β, 17β-diol (Ki=5.4×10-8M) > ethynodiol diacetate (Ki=1.3×10-7M), when taken from Ki. Ki (inhibitor constant) was calculated by the following equation : Ki=iKd/ (Kp-Kd), where Kd is the dissociation constant, i is the concentration of an inhibitor and Kp is the pretending dissociation constant in the presence of an inhibitor.<BR>These results suggest that the 3-ketone and 17β-hydroxyl groups, and the plane of ring A/B of norethindrone are important to bind with progesterone receptor.<BR>2. The uterine cytosols, preincubated with 3H-progesterone (or 3H-norethindrone) alone or in the presence of cold steroids at 4°C for lh 30 min, were incubated with uterine chromatins at 4°C for 1h 30 min. These chromatins were washed, and the radioactivities in them were counted.<BR>It was indicated that the effect of cold steroids of the estrane series on the formation of progesterone- or norethindrone-receptor complex which binds to the chromatin appeared to be similar in their effect on progesterone- or norethindrone-receptor binding.

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