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Mechanisms for altered reproductive function in female rats following neonatal administration of raloxifene.

Tena-Sempere M, Barreiro ML, Aguilar E, Pinilla L.

Department of Cell Biology, Physiology and Immunology, Physiology Section, Faculty of Medicine, University of Cordoba, Avda Menendez Pidal, 14004 Cordoba, Spain.

OBJECTIVE: Raloxifene is a non-steroidal selective estrogen receptor modulator (SERM) that mimics estrogenic activity on bone density and blood lipid concentration without uterotropic actions. Previous data from our laboratory indicated that, as is the case for estrogen, neonatal administration of raloxifene disturbed normal differentiation of the hypothalamic circuitries governing the gonadotropic axis. In contrast, raloxifene did not act in the same way as estrogen does on the neuronal systems controlling sexual receptivity in the female rat. At present, however, the mechanisms for these organizing effects of raloxifene are not completely elucidated. DESIGN AND METHODS: To analyze this phenomenon, female rats were injected daily with raloxifene (50, 100, 250 or 500 microg/rat per day) between days 1 and 5 of age. On day 23, hypothalamic gonadotropin-releasing hormone (LHRH) mRNA expression was assessed, and pituitary and plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were measured in basal and LHRH-stimulated conditions. In addition, LH and FSH responses to ovariectomy were evaluated in raloxifene-treated females. Finally, we monitored the ability of neonatal administration of a potent LHRH agonist ([d-Ala(6),d-Gly(10)]-LHRH ethylamide; 0.01 microg/kg per 12 h on days 1-5) to counteract the effects of raloxifene. RESULTS: Our analyses demonstrated that prepubertal rats (23-day-old females) treated neonatally with raloxifene showed decreased hypothalamic LHRH mRNA expression levels, reduced pituitary content of LH and FSH, reduced basal and LHRH-stimulated LH secretion in vivo and in vitro, and decreased response to ovariectomy. In addition, adult females treated neonatally with raloxifene showed anovulation and reduced serum LH levels; these effects were not prevented by the simultaneous administration of a LHRH agonist. CONCLUSION: In conclusion, our data demonstrate that neonatal administration of raloxifene can disrupt the programming of hypothalamic-pituitary-ovarian axis function. Reduced LH secretion, under basal and LHRH-stimulated conditions and after ovariectomy, is probably related to decreased LHRH expression, reduced pituitary LH content and/or decreased pituitary responsiveness to hypothalamic LHRH.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15012627&dopt=Abstract raloxifene Evista



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Disposition mechanisms of raloxifene in the human intestinal Caco-2 model.

Jeong EJ, Lin H, Hu M.

Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Pullman, Washington 99164-6510, USA.

The purpose of this study was to determine the mechanisms responsible for transport of raloxifene and its hydrophilic conjugates. Human intestinal Caco-2 cell culture model and Caco-2 cell lysate were used for the studies. The results indicated that absorptive permeability (PAB) of raloxifene was lower than its secretory permeability (PAB). As the concentration increased, the efflux ratio (PBA/PAB) decreased, but PBA increased. PAB was also increased in the presence of verapamil and cyclosporine A, two P-glycoprotein inhibitors. Raloxifene was extensively metabolized into sulfated and glucuronidated conjugates. The extent of metabolism or clearance was decreased as the concentration increased from 3.4 (96%) to 30 (22%) microM. Multidrug resistance-related protein inhibitors MK-571 (C26H26ClN2O3S2) and leukotriene C4 significantly decreased (maximal 80%) apical efflux of both conjugates. They also significantly decreased (maximal 85%) basolateral efflux of glucuronides but not sulfates. On the other hand, organic anion transporter (OAT) inhibitor estrone sulfate and estrone glucuronide significantly decreased (maximal 50%) the efflux of sulfate from both sides but had variable effects on glucuronide efflux. Inhibition of conjugate efflux with the OAT inhibitor estrone sulfate was concentration dependent, which resulted in increased transport of intact raloxifene (maximal 90%). This increase in raloxifene transport was also observed in the presence of another OAT inhibitor estrone glucuronide (70%). In conclusion, this is the first report that inhibition of an efflux transporter responsible for the transport of metabolites can result in increase in the transport of the intact compound. It also provides additional explanation why raloxifene has low bioavailability but a long half-life.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15020665&dopt=Abstract raloxifene Evista



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Raloxifene acutely suppresses ventricular myocyte contractility through inhibition of the L-type calcium current.

Liew R, Stagg MA, MacLeod KT, Collins P.

Cardiac Medicine, National Heart and Lung Institute, Imperial College London, Dovehouse Street, London, SW3 6LY.

1. The selective oestrogen (ER) receptor modulator, raloxifene, is widely used in the treatment of postmenopausal osteoporosis, but may also possess cardioprotective properties. We investigated whether it directly suppresses myocyte contractility through Ca(2+) channel antagonism in a similar way to 17beta-oestradiol. 2. Cell shortening and Ca(2+) transients were measured in single guinea-pig ventricular myocytes field-stimulated (1 Hz, 37 degrees C) in a superfusion chamber. Electrophysiological recordings were performed using single electrode voltage-clamp. 3. Raloxifene decreased cell shortening (EC(50) 2.4 microm) and the Ca(2+) transient amplitude (EC(50) 6.4 microm) in a concentration-dependent manner. At a concentration of 1 microm, raloxifene produced a 33+/-2% (mean+/-s.e.m) and 24+/-2% reduction, respectively (P<0.001, n=14 for both parameters). 4. These inhibitory actions were not observed in myocytes that had been incubated with the specific antagonist, ICI 182,780 (10 microm) (n=11). 5. Raloxifene (1 microm) shortened action potential durations at 50 and 90% repolarisation (P<0.05 and <0.001, respectively; n=27) and decreased peak L-type Ca(2+) current by 45%, from -5.1+/-0.5 pA/pF to -2.8+/-0.3 pA/pF (P<0.001, n=18). 6. Raloxifene did not significantly alter sarcoplasmic reticulum Ca(2+) content, as assessed by integrating the Na(+)/Ca(2+) exchanger currents following rapid caffeine application. 7. The present study provides evidence for direct inhibitory actions of raloxifene on ventricular myocyte contractility, mediated through Ca(2+) channel antagonism.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15023859&dopt=Abstract raloxifene Evista



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Raloxifene therapy does not affect uterine blood flow in postmenopausal women: a transvaginal Doppler study.

de Azevedo GD, do Prado MF, Ferriani RA, dos Reis RM, Berezowski AT, Ribeiro TF, Silva E, de Oliveira Maranhao TM, Silva de Sa MF.

Department of Obstetrics and Gynecology, Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, BR 101, Ribeirao Preto, SP, Brazil. georgedantas uol.com.br

OBJECTIVE: To monitor the effects of raloxifene therapy on the uterus of postmenopausal women by transvaginal ultrasonography and color flow Doppler. Methods: Twenty-five healthy postmenopausal women were enrolled in this prospective longitudinal study performed at Department of Gynecology and Obstetrics, Faculty of Medicine of Ribeirao Preto. The patients were treated with raloxifene hydrochloride (60 mg per day) for 6 months. All were submitted to transvaginal ultrasound examination with color flow Doppler (ATL-HDI 3000 equipment) before the beginning and after 1, 3 and 6 months of treatment. Resistance index (RI) and pulsatility index (PI) of the uterine arteries were determined by the Doppler method, being considered as indicators of uterine perfusion. The following variables were analyzed: endometrial thickness, uterine volume, RI, and PI. Data were analyzed statistically by repeated-measures analysis of variance. RESULTS: Before treatment, endometrial thickness was 3.38 +/- 0.73 mm, and similar values were observed after 1, 3 and 6 months of treatment (3.04 +/- 0.82; 3.3 +/- 0.83; and 3.37 +/- 0.79, respectively) (P > 0.05). No significant differences in uterine volume were observed between the pre- and post-treatment periods. Uterine artery perfusion as indicated by RI and PI measured by Doppler also showed no significant variation, with a high impedance flow being maintained throughout treatment. CONCLUSIONS: In the group studied here, raloxifene treatment at the dose of 60 mg per day for 6 months did not induce significant changes in endometrial thickness, uterine volume or uterine artery perfusion, confirming that short-term raloxifene treatment does not affect the uterus of postmenopausal women.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15036489&dopt=Abstract raloxifene Evista



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Comparative study of the short-term effects of a novel selective estrogen receptor modulator, ospemifene, and raloxifene and tamoxifen on rat uterus.

Zheng H, Kangas L, Harkonen PL.

Medicity Research Laboratory, Department of Anatomy, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520 Turku, Finland.

To investigate the differential short-term effects of selective estrogen receptor (ER) modulators (SERMs) on uterus, we treated adult ovariectomized rats with a novel SERM, ospemifene (Osp), two previously established SERMs (tamoxifen and raloxifene (Ral)) and estradiol. The expression of two estrogen-regulated early response genes c-fos and vascular endothelial growth factor (VEGF), and DNA synthesis were analysed at 1-24 h after treatment of ovariectomized rats. Induction of c-fos mRNA by each of the SERMs showed a biphasic pattern with peaks at 3 and 20 h, respectively. The maximum level of VEGF mRNA was observed at 1 h after raloxifene and 6 h after tamoxifen or ospemifene treatment. Maximum levels of the c-fos and VEGF mRNA after raloxifene treatment were higher than those seen after treatments with E2 or a corresponding dose of tamoxifen or ospemifene. DNA synthesis was significantly increased by ospemifene, tamoxifen and raloxifene both in luminal and glandular epithelium. The stimulation was transient, peaking at 16 h. In comparison, the maximum level observed at 16 h after E2 treatment sustained at least until 24 h. DNA synthesis in stromal cells was increased by the SERMs but not by E2 at 24 h. When treated together with E2, the SERMs were able to antagonise E2-stimulated DNA synthesis at 16 h. Our results demonstrate that the initial response of uterus to ospemifene, raloxifene and tamoxifen includes activation of early response genes and even transient stimulation of DNA synthesis in spite of their different long-term effects. However, the early stimulatory events may be mediated by different mechanisms leading to diverging pathways in various tissue compartments and development of differential SERM-specific long-term responses of uterus.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15084346&dopt=Abstract raloxifene Evista



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The effect of raloxifene on markers of bone turnover in older women living in long-term care facilities.

Hansdottir H, Franzson L, Prestwood K, Sigurdsson G.

Department of Geriatrics, Landspitali University Hospital, Reykjavik, Iceland.

OBJECTIVES: To examine the effect of raloxifene on bone turnover in elderly women. DESIGN: Clinical intervention. SETTING: Long-term care facilities. PARTICIPANTS: Nineteen women completed the study, mean age 85 (range 76-99). INTERVENTION: Raloxifene 60 mg was given daily for 12 weeks. MEASUREMENTS: Markers of bone turnover were plasma C-telopeptides of type I collagen (CTx), urine cross-linked N-telopeptides of type I collagen (NTx) and serum tartrate-resistant acid phosphatase (TRAP 5b), plasma osteocalcin, and serum bone alkaline phosphatase. Other markers were serum 25-OH vitamin D, parathyroid hormone, ionized calcium, and phosphate. Markers were measured at baseline, after calcium and vitamin D had been taken for 6 weeks, after raloxifene had been taken for 12 weeks, and 6 weeks after raloxifene had been stopped. Paired sample t test was used to examine changes in markers at each time point. RESULTS: Plasma CTx decreased on average by 31%, urinary NTx by 35%, plasma osteocalcin by 25%, serum bone alkaline phosphatase by 15% (P<.01), and serum TRAP 5b by 10% (P<.05) on treatment. CONCLUSION: Raloxifene reduces bone turnover in elderly women living in long-term care facilities. The effect of raloxifene on bone turnover is comparable with that seen in younger postmenopausal women.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15086661&dopt=Abstract raloxifene Evista