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Claes Ohlsson, Petra Henning, Karin H Nilsson, Jianyao Wu, Karin L Gustafsson, Klara Sjögren, Anna Törnqvist, Antti Koskela, Fu-Ping Zhang, Marie K Lagerquist, Matti Poutanen, Juha Tuukkanen, Ulf H Lerner and Sofia Movérare-Skrtic

mouse model with tamoxifen-inducible efficient global Wnt16 inactivation ( Hayashi & McMahon 2002 ) and determined the effects of WNT16 on cortical bone mass in young adult and old mice. This mouse model is more similar to a systemic modulation of WNT

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Haifan Zhang, Tim McElrath, Wei Tong and Jeffrey W Pollard

have selective effects on hormone responsive tissue and therefore are known as selective estrogen receptor response modulators or SERMs ( Jordan & Morrow 1999 , McDonnell 1999 ). The most successful of them to date is tamoxifen. In large clinical

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The hormonal effects of tamoxifen (10 mg daily for 6 months) have been studied in nine men with oligospermia. Basal concentrations of serum LH (1·7 ± 0·1 (s.e.m.) i.u./l) increased to a maximum of 4·1 ± 1·3 i.u./l (P < 0·001) after 6 months, and FSH rose from 4·9 ± 1·0 to a maximum of 7·7 ± 1·3 i.u./l after 4 months of treatment (P < 0·01).

The response to luteinizing hormone releasing hormone (LH-RH) was studied at monthly intervals. Sums of increments of serum LH increased from 35 ± 4 to 92 ± 17 i.u./l at 4 months (P < 0·001) and of FSH from 14 ± 3·4 to 23 ± 3·5 i.u./l at 4 months (P < 0·01).

Basal serum androgens rose from 25 ± 2·7 to 38 ± 2·4 nmol/l after 4 months of treatment (P < 0·05), and serum oestradiol-17β increased from 185 ± 25 to 631 ± 90 pmol/l by 6 months (P < 0·001). No significant changes occurred in sperm counts.

Five normal men acted as controls: they were given tamoxifen for 1 week. No significant changes were observed in serum LH, FSH or release of these hormones following administration of LH-RH. Serum androgens and oestrogens however, increased significantly by day 4 of treatment (P < 0·05).

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Tamoxifen (ICI 46,474) has been shown to possess anti-tumour properties in the dimethylbenz(a)anthracene (DMBA)-induced rat mammary carcinoma model. During tamoxifen therapy the binding of [3H]oestradiol in vivo to uterine (P < 0·001), vaginal (P < 0·01) and tumour (P < 0·001) tissues was significantly reduced. Tamoxifen therapy was without effect on the binding of [3H]oestradiol in heart tissue. The determination of specific oestrogen-binding components in vitro was significantly reduced (P < 0·01) in tumours from tamoxifen-treated rats and tamoxifen inhibited the binding of [3H]oestradiol to 8S oestrogen-binding components, derived from rat uteri and DMBA-induced tumours, in vitro.

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The oestrogenic and antioestrogenic properties of tamoxifen and its monohydroxylated (monohydroxytamoxifen) and dihydroxylated (dihydroxytamoxifen) metabolites have been investigated in the immature rat. Whether administered orally or subcutaneously, monohydroxytamoxifen was more active than tamoxifen as an antioestrogen. Dihydroxytamoxifen was less active than tamoxifen as an antioestrogen, but this derivative alone was unable to induce a uterotrophic response. Both metabolites of tamoxifen were potent inhibitors of the binding of [3H]oestradiol to oestrogen receptors in vitro. It is possible that the metabolites play a supportive role in the antioestrogenic activity of tamoxifen. The potent activity of monohydroxytamoxifen in vivo and in vitro suggests that this compound could be an important new tool for the subcellular investigation of oestrogenic and antioestrogenic events.

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José E Sánchez-Criado, Carmina Bellido, Rafaela Aguilar and José C Garrido-Gracia

pituitary to oestrogen ( Fink 1988 ) or tamoxifen ( Sánchez-Criado et al. 2004 , 2005 ). The triphenylethylene tamoxifen (TX) is a selective oestrogen receptor (ER) modulator that displays mixed agonist/antagonist activities ( Cosman & Lindsay

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H. K. ADAM, M. A. GAY and R. H. MOORE

A method is described for the determination of tamoxifen in serum. The drug was extracted from the serum and separated from its metabolites by thin-layer chromatography. Irradiation of the thin-layer plate with ultra-violet light after development converted tamoxifen to a fluorescent product which could be estimated in situ by densitometry. The fluorescent product was identified as a substituted phenanthrene by thin-layer chromatography, and gas chromatography–mass spectrometry. The method allowed concentrations as low as 6·8 nmol/l serum to be measured.

After an oral dose of tamoxifen (10 mg) to a female patient the maximum serum concentration (66·2 nmol/l) was achieved in 3 h. When 10 mg tamoxifen were taken twice daily for 21 days by the same patient serum concentrations of about 500 nmol/l were achieved.

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The antioestrogens clomiphene and tamoxifen exhibit both agonistic and antagonistic properties in the rat uterus. The effect of these antioestrogens on RNA polymerase activities in the rat uterus was investigated. Both compounds stimulated an early increase in the activity of endogenous RNA polymerase B similar to that observed after oestradiol treatment. A secondary stimulation of activity of RNA polymerase B was observed after treatment with oestradiol and both antioestrogens. In addition, the activity of endogenous RNA polymerase A was increased initially at 1 h by all three compounds but this activity was maintained at 24 h only by oestradiol.

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R. A. Prysor-Jones, J. J. Silverlight and J. S. Jenkins

The antioestrogenic drug tamoxifen was administered to rats bearing transplanted prolactin-secreting tumours derived from spontaneously occurring pituitary adenomas in Wistar–Furth rats. Some inhibition of tumour growth was observed but this was accompanied by an increase in plasma prolactin concentrations. Bromocriptine, however, consistently inhibited both growth and prolactin secretion of these tumours. The addition of tamoxifen to bromocriptine treatment produced no increased response to the dopamine agonist. Tamoxifen increased prolactin secretion by tumour cells in vitro but did not affect DNA synthesis. Normal rats responded to tamoxifen with a moderate increase in plasma prolactin concentrations and there was no change in pituitary DNA synthesis.

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José C Garrido-Gracia, Ana Gordon, Carmina Bellido, Rafaela Aguilar, Inmaculada Barranco, Yolanda Millán, Juana Martín de las Mulas and José E Sánchez-Criado

( Sánchez-Criado et al. 2004 , 2006 a ). Tamoxifen (TX), a type I oestrogen antagonist with selective ER modulator (SERM) properties ( McDonnell 1999 , 2003 , McDonnell et al. 2002 , Smith & O’Malley 2004 ), exhibits agonist activities in the