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Studies on sex organ development. Effect of hormones on ornithine decarboxylase activity in the developing chick ovary.

ABSTRACT: The response of ornithine decarboxylase activity to hormones in the embryonic left ovary was measured throughout the stages of development. During the early stage of ovarian development (9th day of incubation), the ornithine decarboxylase activity (in terms of pmol CO(2)/30min per mg of protein) was high (766); it decreased from the 10th to the 12th day (575-239), increased slightly from the 13th to the 15th day (306) and finally fell to a low value (192-20) from the 18th day of development to birth. Administration of an optimal dose of oestrogen to the 9-10-day embryo stimulated the ovarian ornithine decarboxylase activity by 48-53%. If the same dose of oestrogen was administered to the 15-18-day embryo, the ovarian enzyme activity was suppressed by 32-43%. This biphasic response to oestrogen for enzyme induction is characteristic of the developing ovary and is not observed in other genital organs of the chick. In the early developmental stage (9-10th day) testosterone has no effect on ovarian ornithine decarboxylase activity, but in the late stage testosterone inhibits the activity by 41%. Organ culture techniques have been used to test the ovarian response to lutropin (luteinizing hormone). Lutropin stimulated ornithine decarboxylase activity by approx. 99-155% in the ovary of the early embryonic stage (10-13th day), and by 175-200% in the ovary of the late embryonic stage (15-18th day). The alteration in enzyme activity in the ovary as assayed in vitro during development is not due to the effect of the size of the endogenous ornithine pool. The relationship of ornithine decarboxylase activity to the morphological and biochemical changes in the developing ovary is discussed.

SUBMITTER: Teng CS

PROVIDER: S-EPMC1161872 | biostudies-other | 1980 May

REPOSITORIES: biostudies-other

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Project description:The prostate is a male accessory sex gland that produces secretions in seminal fluid to facilitate fertilization. Prostate secretory function is dependent on androgens, although the mechanism by which androgens exert their effects is still unclear. Polyamines are small cationic molecules that play pivotal roles in DNA transcription, translation and gene regulation. The rate-limiting enzyme in polyamine biosynthesis is ornithine decarboxylase, which is encoded by the gene Odc1. Ornithine decarboxylase mRNA decreases in the prostate upon castration and increases upon administration of androgens. Furthermore, testosterone administered to castrated male mice restores prostate secretory activity, whereas administering testosterone and the ornithine decarboxylase inhibitor D,L-α-difluromethylornithine (DFMO) to castrated males does not restore prostate secretory activity, suggesting that polyamines are required for androgens to exert their effects. To date, no one has examined polyamines in prostate development, which is also androgen dependent. In this study, we showed that ornithine decarboxylase protein was expressed in the epithelium of the ventral, dorsolateral and anterior lobes of the adult mouse prostate. Ornithine decarboxylase protein was also expressed in the urogenital sinus (UGS) epithelium of the male and female embryo prior to prostate development, and expression continued in prostatic epithelial buds as they emerged from the UGS. Inhibiting ornithine decarboxylase using DFMO in UGS organ culture blocked the induction of prostatic buds by androgens, and significantly decreased expression of key prostate transcription factor, Nkx3.1, by androgens. DFMO also significantly decreased the expression of developmental regulatory gene Notch1. Other genes implicated in prostatic development including Sox9, Wif1 and Srd5a2 were unaffected by DFMO. Together these results indicate that Odc1 and polyamines are required for androgens to exert their effect in mediating prostatic bud induction, and are required for the expression of a subset of prostatic developmental regulatory genes including Notch1 and Nkx3.1.

Project description:The effects of diethylstilboestrol on morphogenesis and cyto-differentiation of the chick-embryo left Müllerian duct were examined. Embryos were treated at different stages of development with maximal-responsive doses of diethylstilboestrol over a 5-day interval. The shell gland and magnum regions of the Müllerian duct were then assayed for growth and histological morphogenesis. The results were correlated with diethylstilboestrol-induced ovalbumin-gene expression as measured by ovalbumin-mRNA (mRNAov) accumulation and the relative rate of ovalbumin synthesis. Treatment of the embryo from day 10 to day 15 of incubation induces morphogenesis of tubular-gland cells in the Müllerian-duct magnum. Although these cells constitute 10% of the total cell population and contain an average of 8000 molecules of mRNAov per cell, ovalbumin synthesis is only 0.85% of total magnum protein synthesis. The Müllerian-duct magnum of embryos treated from day 13 to day 18 of incubation contains about 30% tubular-gland cells, which have accumulated an average of 7000 molecules of mRNAov per cell, but ovalbumin synthesis is only 3.25% of total magnum protein synthesis. The Müllerian-duct magnum of embryos treated from day 16 to day 21 of incubation contains about 50% tubular-gland cells, which have accumulated an average of 6500 mRNAov molecules per cell, and ovalbumin synthesis is 10% of total magnum protein synthesis. Oestrogen responsiveness develops simultaneously in the Müllerian-duct magnum and shell-gland regions. Compared with the rate of diethylstilboestrol-induced oviduct growth, the relative rate of diethylstilboestrol-induced Müllerian-duct growth increases with embryonic age, from 20-fold lower in the 10-day embryo to only 3-fold lower in the 16-day embryo. All results are discussed in comparison with the responses to oestrogen of the immature chick oviduct, and in terms of the ontogeny of hormone-competent epithelial and stromal components of the Müllerian duct. It is concluded that the development of oestrogenic competence in the embryonic Müllerian duct is a multiphasic phenomenon. A dramatic increase in hormone responsiveness in the Müllerian duct occurs between days 10 and 16 of development, and a less dramatic final maturation of oestrogen responsiveness occurs between day 16 of development and 1 week after hatching.

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Studies on sex organ development. Effect of hormones on ornithine decarboxylase activity in the developing chick ovary.

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