Estradiol, role

Shore, L.S., Shemesh, M., and Cohen, R. (1988). The role of estradiol and estrone in chicken manure silage in hyperestrogenism in cattle. Australian Veterinary Journal 65, 68-68. 

Estrogens are also neuroprotective against ischemic damage [13], and aromatization of androgens to estrogens plays a role even in females, where knockout of the aromatase gene increases the vulnerability of female mice to stroke damage by a process that is prevented by estradiol administration [33]. 

Tebar M, Bellido C, Aguilar R, Sanchez-Criado JE (1994) Inappropriate ovarian feedback in basal gonadotropin secretion in 4-day cyclic rat treated with mifepristone role of endogenous estradiol. J Endocrinol Invest 17 425-430... 

The stereospecificity of hydrogen transfer for estradiol-17 and estradiol-17(3 dehydrogenases has been examined by George et a/.84>. These enzymes are both present in chicken liver, and have substrates which differ only in the chirality of their substituents at C—17. Both of these enzymes were shown to use the 4-pro-S or 4B proton of the NADPH. Since the steroid is a bulky substrate, the authors argue that the steric fit between pyridine nucleotide and steroid cannot be as important as the role played by the enzyme in directing the fit. This paper contains an interesting summary of other recent work on the stereospecificity of pyridine nucleotide dependent-steroid dehydrogenases. 

As expected, in vitro transcription assays involving PARP-1, NAD, and PARC illustrate these predicted outcomes (Kim et al, 2004). Even when driven by a transcriptional activator, such as estradiol-bound estrogen receptor, transcription is repressed when PARP-1 is added to chromatin templates. The repression is reversed by NAD+, and the NAD+-dependent effects are reversed by PARC (Kim et al, 2004). This system for transcriptional control shifts new importance onto the enzymes responsible for synthesis of NAD+ in the nucleus, such as nicotinamide mononucleotide adenylyltransferase-1 (Magni et al, 2004). Because NAD+ facilitates the decompaction of chromatin and the derepression of transcription, nuclear NAD+ biosynthetic enzymes may play critical roles as cofactors. 

The biologically inactive estrone sulfate (EIS) and dehydro-epiandrosterone-sulfate (DHEAS) are the most abundant circulating estrogenic precursors in the plasma of post-menopausal women [103]. Desulfation of inactive steroid-3-0-sulfates by estrone-sulfatase (STS) plays a key role in the regulation of levels of receptor-active estrogenic steroids (estradiol and androstenediol) in breast cancer cells (Fig. 9). There is strong evidence suggesting that estrone sulfatase (STS) and DHEA-sulfatase are the same enzyme [103]. 

CYP1A2 is known to play a significant role in the metabolism of aromatic amines, estradiol, and other drugs. Furthermore, it is known that CYP1A2 is induced by cigarette smoke and charcoal-broiled meat. 

A similar mechanism has been found for 17(3-hydroxysteroid dehydrogenase (17(3-HSD), the enzyme that regulates the concentrations of estradiol and testosterone in human [5,16,17] (Figure lb). Genetics diseases associated with mutations in this enzyme lead to developmental abnormalities [18]. Enzymes that regulate the concentrations of retinoids [19] and prostaglandins [20] may also have a similar role [6]. 

Two female sex hormones, estradiol-17 and progesterone, and one male sex hormone, testosterone, are used as growth promoters on beef cattle (Fig. 7.1). By nature, they are all endogenous products playing an important role in controlling reproductive functions in humans and animals. When applied exogenously they will enter the same metabolic pathways as the endogenously produced molecules. 

Terrazas, L.I., Bojalil, R., Covezensky, T. and Larraide, C. (1994) A role for 1 7-(3-estradiol in immunoen-docrine regulation of murine cysticercosis (Taenia crassiceps). journal of Parasitology 80, 563-568. 

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