Hormonale Enzyminduktion im Myometrium. Beispiel einer Oestrogenwirkung am Erfolgsorgan

Summary

The reversible oxidation of estradiol-17β to estrone is catalysed in the myometrium of rabbits, a target organ of estrogens, by a 17β-hydroxysteroid: NAD(P) oxidoreductase. The specific activity of this enzyme rises in pregnancy and after the administration of estrogenic hormones. The non steroidal estrogenic hormone diethylstilboestrol is as effective as estradiol-17β and causes approximately the 50-fold increase of activity compared with that of normal adult rabbits. No change of activity is found in liver and kidney and after the administration of progesterone and testosterone in the myometrium. About 7 to 10 hours after administration of estradiol-17β the activity of the 17β-hrydroxysteroid oxidoreductase in the myometrium begins to increase. The lowest amount of estradiol-17β which is necessary is 1 μg/kg b. w. The peak of increase is reached within 40 hours after the administration of the hormone. The increase of activity in the myometrium is completely inhibited by actinomycin D, puromycin and U 11100 A. The enzyme from the myometrium of pregnant rabbits and castrated animals, which are treated with estradiol-17β or diethylstilboestrol, can be purified about 40-fold. After purification the enzyme has a substrate specifity for estradiol-17β. In the purified extracts one can find a small estradiol dependant transhydrogenation from NADPH to NAD⁺. The ratio dehydrogenase activity: transhydrogenase activity is 11:1. The cause and the meaning of the estrogen dependant increase of activity of the 17β-hydroxysteroid oxidoreductase in the myometrium will be discussed.

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