Vancomycin-Resistant Enterococci in Patients Attending for Colonoscopy: An Estimate of Community Prevalence.

Aims Ireland has the highest vancomycin-resistant Enterococcus faecium (VRE) bloodstream infection prevalence in Europe. Two patterns of VRE carriage are recognised. European, with widespread community prevalence and North American, where carriage is predominantly nosocomial. It is unclear which pattern is dominant in Ireland. This uncertainty limits infection control measures. This study sought to explore this issue via a cross sectional point prevalence study. Methods Asymptomatic community volunteers, represented by patients undergoing elective outpatient colonoscopy testing, were opportunistically screened for VRE. Demographic and risk factor data were collected via a patient survey. Rectal swabs were collected before colonoscopy and VRE was identified using the VITEK MS system. Results 102 patients were cultured. A single patient tested positive, representing a prevalence rate of 0.98% (95% CI <0.01-5.8%). This patient demonstrated traditional risk factors, suggesting nosocomial rather than community acquisition. 94% (N=94) of patients had no knowledge of VRE, while 83% (N=83) had low levels of concern regarding hospital acquired infections. Conclusion There is a low incidence of VRE in the Irish community setting, in contrast to other European Countries, suggesting asymptomatic community colonization is not responsible for the high rates of VRE seen in Ireland. Wider screening or atypical infection control measures would not be supported by this data.

Allergic responses induced by goat milk αS1-casein in a murine model of gastrointestinal atopy.

Up to 3% of young children develop milk allergy and this may influence the development of immune-mediated diseases in later life. One protein that has been associated with allergic reactions to ruminant milk is α(S1)-casein (CN). Studies suggest that goat milk with low levels of α(S1)-CN may reduce allergenicity of milk, but the dose response to α(S1)-CN has not been confirmed. In this study, we examined the immune response to varying levels of goat α(S1)-CN in a mouse model of gastrointestinal allergy. BALB/c mice (aged 5 wk) were given intraperitoneal injections with α(S1)-CN and aluminum as adjuvant at 1 and 3 wk to sensitize mice to the antigen. In wk 5, groups of fasting mice (n=8/group) were challenged 4 times on alternate days by intragastric gavage with saline or 2, 10, or 20mg of α(S1)-CN. Serum levels of specific IgE, IgG(1), and IgG(2a) antibodies and mouse mast cell protease-I were determined. Interleukin-4, IL-10, and IFN-γ responses to 48-h activation with antigen were measured in cultured splenocytes. We determined that mice sensitized with α(S1)-CN had higher titers of specific IgG(1) and IgE antibodies compared with controls; however, groups challenged with differing doses of α(S1)-CN did not differ. The group challenged with the highest dose of α(S1)-CN had a 10-fold increase in mouse mast cell protease-I compared with the group challenged with saline. Both IL-4 and IL-10 were produced in a dose-dependent manner by cultured splenocytes incubated with α(S1)-CN. Overall, α(S1)-CN stimulated the production of cytokines associated with allergic disease in a dose-dependent manner. Thus, milk with lower levels of α(S1)-CN should contribute to a lesser antigenic burden.

Suppression of mouse mammary tumorigenesis by long-term tamoxifen therapy.

A sustained release of tamoxifen, which produced decreasing serum levels of this drug (24 to 4 ng/mL) over 6 months, suppressed mammary tumorigenesis in virgin or once pregnant C3H/OUJ female mice. Tamoxifen was consistently more effective than early ovariectomy, which only delayed tumorigenesis. Tamoxifen prevented the stimulatory action of cyclical (alternate-month) progesterone administration on mouse mammary tumorigenesis. However, when tamoxifen treatment (12 months) was stopped, progesterone treatment initiated tumorigenesis. In contrast, when long-term tamoxifen treatment was stopped in mice that had not undergone ovariectomy, and estrous cycle returned, the majority of these mice remained tumor free. A comparison of different durations (3, 6, and 12 months) of tamoxifen treatment of virgin mice, starting at approximately 4 months of age, showed an equivalent effect on mammary tumorigenesis. All virgin mice developed tumors by 18 months of age, whereas 80% of the tamoxifen-treated mice were tumor free. Nevertheless, cyclical progesterone administration caused rapid development of tumors after 3 months of tamoxifen treatment; only 15% of these mice were tumor free at 18 months. Cyclical progesterone administration caused an increase in tumorigenesis after 6 months of tamoxifen treatment; 50% of these mice were tumor free at 18 months of age. These data demonstrate the efficacy of tamoxifen to suppress mouse mammary tumorigenesis and demonstrate that continuous tamoxifen therapy is necessary to prevent the development of tumors by progesterone, a stimulatory hormone.

Investigation of the mechanism of tamoxifen-stimulated breast tumor growth with nonisomerizable analogues of tamoxifen and metabolites.

BACKGROUND: The nonsteroidal anti-estrogen tamoxifen (TAM) is the front-line endocrine treatment for breast cancer, but disease recurrence is common. Treatment failure may occur because tumors become insensitive to TAM. Alternatively, resistance may occur because tumors become stimulated rather than inhibited by TAM. TAM-stimulated growth of MCF-7 human breast tumors has been observed in athymic mice after prolonged treatment with TAM. PURPOSE: Our purpose was to examine the mechanism of treatment failure by determining whether TAM-stimulated tumors acquire the ability to excrete TAM and its anti-estrogenic metabolites or to convert them to estrogenic compounds with weakened antiestrogenic activity. METHODS: We used high-pressure liquid chromatography to quantitate TAM and its metabolites in serum and tumors from ovariectomized athymic mice and in MCF-7 cells grown in vitro. We treated tumor-bearing mice with subcutaneous sustained-release preparations of estradiol, TAM, or a nonisomerizable (fixed-ring) analogue and then assessed the activity of these compounds on TAM-inhibited parental MCF-7 tumors and on TAM-stimulated MCF-7 TAM tumors. RESULTS: We found negligible differences in intratumoral TAM levels between TAM-inhibited parental MCF-7 tumors and TAM-stimulated MCF-7 TAM variants. We did not detect metabolite E (Met E), an estrogenic TAM metabolite, in serum or tumors. Using MCF-7 cells in vitro, we determined that the (Z) isomer of Met E, the form directly produced by TAM metabolism, must be present in the cell at a concentration of over 1000 ng/g to overcome growth inhibition by physiological levels of TAM and antiestrogenic metabolites, but the (E) isomer of Met E was effective at 10 ng/g. We reasoned that conversion of Met E from the (Z) (a weak estrogen) to (E) isomer (a potent estrogen) would be required if formation of Met E were responsible for TAM-stimulated growth. However, fixed-ring TAM, which can only form (Z) Met E, was shown to be as capable as TAM of initiating and maintaining anti-estrogen-stimulated growth of MCF-7 tumors in athymic mice. CONCLUSION: Metabolism and isomerization of TAM to estrogenic compounds is not the mechanism of TAM-stimulated growth in our model. IMPLICATION: Other potential mechanisms for TAM-stimulated growth, such as estrogen receptor mutation, must be investigated so that effective strategies can be devised to control breast cancer once therapy fails.

Alteration of endocrine parameters in premenopausal women with breast cancer during long-term adjuvant therapy with tamoxifen as the single agent.

Tamoxifen is used to treat selected patients at each stage of breast cancer. Although most clinical experience has been obtained with postmenopausal women, increasing numbers of premenopausal women will be treated with 5 or more years of adjuvant tamoxifen therapy following surgery. Indeed, the proposed use of tamoxifen to prevent breast cancer in high-risk women could result in its extended use during the childbearing years. We have monitored the changes in circulating hormone levels from the ovary and pituitary gland in premenopausal (41-47 years old) women with stage I or II breast cancer during adjuvant therapy with tamoxifen as the single agent for 4-72 months following a mastectomy. Each patient (total eight) continued to menstruate, and ovulation occurred. Circulating levels of luteinizing hormone and follicle-stimulating hormone (except in one woman) remained in the normal range (determined in 12 regularly menstruating women in a control group). The levels of estradiol, estrone, and progesterone were elevated onefold to threefold. Prolactin levels decreased by 30%-40%, but the levels of sex hormone binding-globulin were unaffected. These data demonstrate that premenopausal women taking tamoxifen are potentially at risk for pregnancy and must be counseled about barrier contraception. Furthermore, the impact of many years of ovarian stimulation by tamoxifen must be evaluated, especially in women with node-negative disease or in healthy women in whom tamoxifen is used to prevent breast cancer.

Point mutation of estrogen receptor (ER) in the ligand-binding domain changes the pharmacology of antiestrogens in ER-negative breast cancer cells stably expressing complementary DNAs for ER.

The antiestrogen tamoxifen is used in the treatment of hormone-responsive breast cancer. However, therapeutic failure has frequently been observed in both patients and animal models after long term treatment. We have studied the effect of a point mutation that leads to the substitution of Val for Gly at codon 400 in the ligand-binding domain of the estrogen receptor (ER) on estrogenic and antiestrogenic activities of 4-hydroxytamoxifen (4-OHT) and its derivatives. Stable ER transfectants derived from MDA-MB-231 CL10A, an ER-negative breast cancer cell line, have been used in these studies. 4-OHT and its fixed ring derivatives showed more estrogen-like activity in ER transfectants than in MCF-7, an ER-positive breast cancer cell line. In this study, 4-OHT was a partial agonist of cell growth in the transfectant S30 cells, which express the wild-type ER. However, it was a full agonist in the mutant ER transfectant ML alpha 2H, which expressed ER with Val at codon 400. The increased estrogenic activity of 4-OHT in ML alpha 2H cells was not due to the preferential isomerization of trans 4-OHT to cis 4-OHT, since the nonisomerizable fixed ring trans 4-OHT was a partial agonist for cell growth in S30 cells and was a full agonist in ML alpha 2H cells. Transient transfection using a reporter plasmid containing an estrogen response element demonstrated that fixed ring trans 4-OHT had estrogenic activity in ML alpha 2H cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Estrogenic actions of RU486 in hormone-responsive MCF-7 human breast cancer cells.

Previously, we demonstrated that the progestin components (19-nortestosterone derivatives) in oral contraceptives are able to stimulate human breast cancer cell proliferation via an estrogen receptor (ER)-mediated mechanism. We now examine RU486, an antiprogestin, to determine whether it has estrogenic properties because it is also a 19-nortestosterone derivative. We found that RU486 stimulated the growth of MCF-7 human breast cancer cells at a concentration of 10(-6) M, which is similar to the pharmacological concentration (micromolar range) found in women taking RU486. The antiestrogens 4-hydroxytamoxifen and ICI 164,384 blocked RU486-induced cell proliferation. The estrogenic activity of RU486 is not due to impurities or aromatization to estrogenic metabolites. To determine whether the proliferative action of RU486 was mediated through the ER, cells were transfected with a chloramphenicol acetyltransferase reporter gene under the control of an estrogen response element derived from the Xenopus laevis vitellogenin 2A gene. We found that RU486 was able to induce chloramphenicol acetyltransferase activity at the concentrations that stimulated cell proliferation, and this induction was blocked by the addition of 4-hydroxytamoxifen and ICI 164,384. The estrogenic potential of RU486 to regulate ER target gene expression was also investigated. We found that, like 17 beta-estradiol (E2), RU486 was able to alter the expression and synthesis of progesterone receptor. The level of progesterone receptor (145 and 186 fmol/mg cytosol protein, respectively) was increased significantly compared to the control value (3 fmol/mg cytosol protein) with the addition of 10(-6) M RU486 or 10(-10) M E2, as determined by an enzyme immunoassay. The levels of transforming growth factor-beta 2 (TGF beta 2) and TGF beta 3 mRNA, but not TGF beta 1 mRNA, were decreased dramatically with the addition of 10(-6) M RU486. This is consistent with the effects of E2 on TGF beta expression. Therefore, RU486 has estrogen-like activities in its regulation of ER target gene expression. These results demonstrate that RU486 is a weak estrogen in human breast cancer cells and suggest that the RU486-induced cell proliferation is mediated via ER. The novel finding that RU486 exhibits some estrogen-like activity may be important for the interpretation of its action at high dosages as an abortifacient and also if RU486 is going to be evaluated clinically, again at high doses, for the treatment of breast cancer.

Tamoxifen metabolites in patients on long-term adjuvant therapy for breast cancer.

Serum concentrations of tamoxifen, 4-OH-tamoxifen, N-desmethyltamoxifen, and metabolites E and Y were assayed to assess the variation of tamoxifen-metabolism during short-term and long-term endocrine treatment for breast cancer. Once steady-state was achieved, serum levels of tamoxifen and its metabolites in individual patients were stable in the short (10 weeks) and long term (over 7 years) (coefficient of variation [CV], 10-15%), but the variation between individuals (CV 50-70%) was high. Serum tamoxifen and N-desmethyltamoxifen levels were not correlated with indices of obesity. Thus this does not explain the large variation between individuals. In addition to the metabolites that were measured, 4-hydroxy-N-desmethyltamoxifen was tentatively identified in patients' serum. Overall, this study demonstrated that the metabolites of tamoxifen are stable (i.e. no metabolic tolerance) for up to 10 years of drug administration.

Direct measurements of Ab and Ac using vertex and kaon charge tags at the SLAC detector.

Exploiting the manipulation of the SLAC Linear Collider electron-beam polarization, we present precise direct measurements of the parity-violation parameters A(c) and A(b) in the Z-boson-c-quark and Z-boson-b-quark coupling. Quark-antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLAC Large Detector charge coupled device vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-1998 sample of 400 000 Z decays, produced with an average beam polarization of 73.4%, we find A(c)=0.673+/-0.029(stat)+/-0.023(syst) and A(b)=0.919+/-0.018(stat)+/-0.017(syst).

The experience of women with primary biliary cirrhosis: a literature review.

Primary biliary cirrhosis (PBC) is a serious and life-threatening illness that mainly affects women. Epidemiological data on the prevalence of the illness are unclear. The experience of women with this chronic illness has not been explored within nursing research. A review of the literature concerning PBC therefore is based on general themes relating to chronic illness. A chronic illness has two meanings: the symbolic significance and the consequences for the individual. The symbolic significance of PBC can be related to symbolism relating to the liver in general and to the general assumption that liver disease is related to alcohol consumption. The consequences for the individual woman with PBC have been described as following a disease management trajectory. This may include appreciating the major symptoms of the illness. The main symptoms of PBC are fatigue and pruritus. These are both insidious and debilitating symptoms of unclear aetiology that can cause women with PBC problems when seeking an illness explanation. The symptoms may also interfere with the woman's body image and her caring role. It is suggested that the factors that relate to PBC may result in social isolation for women with the illness.

Development, labour relations and gender in Papua New Guinea.

PIP: The increase in wage labor in the periurban village of Siar, Papua New Guinea, was examined by carrying out field work in 1980. There were 82 households in Siar: 40 (49%) had at least one wage earner, and of these, 8 (20%) had two or more wage earners. This was far less than in urban areas (86%) and far more than in rural villages (6%). 39 males aged 20-49 years and 10 females aged 10-29 years out of the total population of 503 people were in regular employment. 6 of the 9 women between the ages of 18 and 25 were employed as clerks, 2 as domestic servants, and 1 as a shop assistant. 6 of the 21 men between the ages of 18 and 25 were employed as clerks, 6 as laborers in a timber mill, 4 as construction workers, 2 as medical assistants, 2 as plantation workers, and 1 in a bakery. 67% of the women were in skilled employment compared with 51% of men. Most Siar villagers were employed in Madang town with 26 people being employed in private enterprise, 17 employed by the government, and 6 by the Lutheran Mission. Access to employment depended largely on the wantok system of referring kinfolk by people who were employed. In contrast to male employment patterns, there was little opportunity for unskilled females. Most wage laborers were unable to save money because of the demands exerted on them by relatives. The villagers had developed needs to be satisfied by monetized transactions: food, clothing, housing materials, school fees, transport costs, and social activities for beer and cigarettes. On the other hand, several women requested that their employers deduct 15% of their wages for savings. The expenditure for food varied between 38% and 58% of the total cash income of units of villagers. The village's population increased because migrants arrived. In 1977, 247 (37%) Siar villagers were absent, most having left for reasons related to employment. Sexual division in Siar reinforced women's alienation from the means of production and they became doubly subordinated to capital and to men.^ieng

A microcomputer application for managing information used when weaning patients from mechanical ventilation.

This article describes a microcomputer application designed to manage data collected from patients assessed for weaning from mechanical ventilation. The application has menu options for obtaining individual summaries of serial weaning assessments. These summaries provide an overview of patients' progress during the weaning process. Users also have the option of obtaining information about procedures and problems often encountered during weaning. In addition, weaning summary data are easily transferred to mainframe computers for statistical analyses. The application is an efficient data manager and provides information that can be used during the patient care decision process, for staff and student instruction, and for research purposes.

Perceived stress in medical, law, and graduate students.

Students in the medical and law schools and graduate students in chemistry and psychology at a single institution were asked to complete a questionnaire about events and activities related to their educational programs which they perceived to be stressful. The questionnaire was designed to elicit information about stress associated with academic activities, personal relationships, time pressures, and financial concerns. Information was also obtained about time utilization, health behaviors, crises, and support systems. The authors' hypothesis that medical students would report higher perceived stress levels than students in the other programs was not supported, as the highest total stress score was reported by law students. Factor analysis of a 31-item stress scale produced six separate factors pertaining to the sources of stress: academic concerns, time concerns, fear of failing, classroom interactions, economic issues, and world issues. Time restrictions and economic and academic issues had the highest mean stress scores. The hypotheses by the authors that students would report program-specific stresses and that utilization of support services would differ among the four groups of students were both supported. Implications of these findings are discussed.

Weaning from mechanical ventilation: a method for assessment and planning.

Weaning patients from mechanical ventilator assistance is difficult and often requires the input of experts. Though researchers have identified numerous factors that impede weaning and continue to develop criteria to determine ability to wean, no single factor or set of criteria have yet emerged to guide clinicians. In an effort to design a tool that assists critical care nurses in forwarding the wean process, the authors developed a comprehensive, integrated, computerized ventilator weaning program that stimulates the thinking and care planning strategies of experts. The Burns Wean Assessment Program also teaches complex concepts and tracks the progress of the weaning patient.

Studies of tamoxifen as a promoter of hepatocarcinogenesis in female Fischer F344 rats.

Tamoxifen, an antiestrogen used in the treatment of breast cancer, was assessed for carcinogenic potential in the two-stage model of experimental hepatocarcinogenesis. Groups of female Fisher F344 rats were initiated with a non-necrogenic, subcarcinogenic dose of diethylnitrosamine (DEN; 10 mg/kg, po) and fed tamoxifen at a concentration of 250 mg per kg of AIN-76A diet for 6 or 15 months. The livers of these animals exhibited an increase in size and number of altered hepatic foci compared with those animals which were initiated with DEN but not exposed to tamoxifen. This finding indicates that tamoxifen may have a carcinogenic potential in the rat liver. After 6 months of treatment, neoplastic nodules were observed in 3/8 rats in the DEN-initiated, tamoxifen-treated group. In the initiated group provided with tamoxifen for 15 months, neoplastic nodules were observed in 7/8 rats and hepatocellular carcinomas in 3/8 rats. The serum level of tamoxifen in these rats was 200-300 ng/ml. The ratio of tamoxifen, 4-hydroxy tamoxifen, and N-desmethyl tamoxifen was 1:0.1:0.5-1 in the serum. When adjusted for age-related weight increases, the serum and liver levels of tamoxifen and its N-desmethyl metabolite did not change over the 15 months. In the rat liver, the level of tamoxifen and its N-desmethyl metabolite was 10-29 micrograms/g liver after 6 or 15 months of chronic dietary administration. The ratio of tamoxifen:4-hydroxy tamoxifen:N-desmethyl tamoxifen was 1:0.1.3-3.3 in the liver. Therefore, the liver had 20- to 30-fold more tamoxifen and 4-hydroxy tamoxifen and at least 100-fold more N-desmethyl tamoxifen than the serum (assuming 1 gram of tissue is equivalent to 1 ml of serum). These results indicate that tamoxifen is a promoting agent for the rat liver at serum levels found in patients given the usual therapeutic course of tamoxifen. The high concentrations of tamoxifen attained in the rat liver indicate that actions other than its known estrogenicity for liver could contribute to its promoting action. In addition, these results indicate that the pharmacodynamic differences in tamoxifen metabolism in rats and humans and at low versus high doses should be determined. Thus, the therapeutic indications for tamoxifen should be balanced by the potential risk it may present as a promoting agent in mammalian liver.

The effect of tamoxifen and two of its non-isomerizable fixed-ring analogs on multistage rat hepatocarcinogenesis.

Long-term treatment of breast cancer patients with tamoxifen has prompted concern over potential toxicity of this drug with chronic administration. Since tamoxifen has estrogenic action in the rat liver and estrogenic agents can increase hepatoma incidence in rats, tamoxifen and two non-isomerizable, fixed-ring analogs (FRT1 and FRT2) were evaluated as promoting agents in a two-stage model of hepatocarcinogenesis in female Fischer F344 rats. The rats were subjected to 70% partial hepatectomy and half of the animals were administered the initiating agent, diethylnitrosamine (DEN; 10 mg/kg body wt), while the other half were not initiated. Groups of initiated and uninitiated animals were allowed to recover for 2 weeks and were then administered tamoxifen or one of the fixed-ring analogs admixed into AIN-76A diet at 25, 100 or 250 mg/kg diet. After 6 months of anti-estrogen administration the rats were sacrificed and uterine weights, blood levels of anti-estrogen, and liver histopathology were assessed. Uterine weights were decreased 2- to 3-fold by each of the agents, consistent with an anti-estrogenic action in the rat. The serum levels in rats administered 250 mg anti-estrogen/kg diet for 6 months were 320+/-20 ng/ml for tamoxifen, 320+/-10 for FRT1 and 350+/-20 for FRT2. The liver levels after a 6 month administration of 250 mg anti-estrogen/kg diet were 13 870+/-860 ng/g for tamoxifen, 13 300 +/-860 for FRT1 and 26 900+/-1900 for FRT2. A dose-dependent increase in serum and liver level of each compound was noted when measured at the 6 month time period. The number and percentage of the liver occupied by altered hepatic foci (AHF) were determined by quantitative stereology. A dose-dependent increase above initiated controls was observed in the initiated, tamoxifen-treated rats. Both fixed-ring analogs also increased the number and size of AHF compared with initiated controls, but were less potent than tamoxifen, suggesting that tamoxifen has an intrinsic promoting action in the liver that is independent of its ability to isomerize to more potent estrogenic compounds. In addition, the fixed-ring analogs have a weaker promoting activity in the rat liver than does tamoxifen. This may be due to pharmacokinetic differences at the lower two doses, but it is independent of achieved serum level at the highest dose and hence may reflect differences in intrinsic activity of these compounds. Thus tamoxifen and the two fixed-ring analogs promote the development of rat hepatocarcinogenesis.

Metabolites, pharmacodynamics, and pharmacokinetics of tamoxifen in rats and mice compared to the breast cancer patient.

The metabolism of tamoxifen was examined in the rat, mouse, and human breast cancer patient. Large oral doses of tamoxifen (200 mg/kg) in the immature ovariectomized rat and mature mouse produced circulating levels of the parent compound, N-desmethyltamoxifen, and 4-hydroxytamoxifen quantifiable by HPLC separation, UV activation, and fluorescence detection. N-Desmethyltamoxifen and 4-hydroxytamoxifen serum levels in the mature ovariectomized mouse paralleled tamoxifen levels throughout a 96-hr time course after a single dose of tamoxifen. On the other hand, N-desmethyltamoxifen was the predominant serum metabolite after an equivalent dose of tamoxifen to the immature rat, but there was little 4-hydroxytamoxifen. Peak levels of tamoxifen occurred 3-6 hr after oral administration of tamoxifen in both species, whereas peak levels of N-desmethyltamoxifen in the immature rat did not occur until 24-48 hr. AUCs for tamoxifen and N-desmethyltamoxifen were approximately 4 times greater in the rat (57.5 and 111 micrograms.hr/ml, respectively) than the mouse (15.9 and 26.3 micrograms.hr/ml, respectively) after equivalent doses of tamoxifen (200 mg/kg). AUC of 4-hydroxytamoxifen for the rat (8.9 micrograms.hr/ml), however, was similar to that for the mouse (13.9 micrograms.hr/ml). The rate of elimination from serum was similar for tamoxifen, N-desmethyltamoxifen, and 4-hydroxytamoxifen in both the rat (t1/2 = 10.3, 12.1, and 17.2 hr, respectively) and the mouse (t1/2 = 11.9, 9.6, and 6 hr, respectively). Administration of large oral doses of tamoxifen (200 mg/kg) every 24 hr to mature ovariectomized mice or immature ovariectomized rats resulted in accumulation for the first 4 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure-function relationships of hydroxylated metabolites of tamoxifen that control the proliferation of estrogen-responsive T47D breast cancer cells in vitro.

Several hydroxylated derivatives of tamoxifen were tested for their effects on the growth of T47D human breast cancer cells in vitro. Compounds containing a fused seven-membered ring were used to prevent isomerization of the triphenyl-ethylenes at the double bond. This stable structure permitted the determination of the activity of the cis and trans forms of tamoxifen and the true activity of two of its metabolites, 4-hydroxytamoxifen and metabolite E. Estradiol stimulates the growth of T47D cells 3-4-fold over control after 6 days of treatment (EC50 = congruent to 3 x 10(-12) to 3 x 10(-11) M, depending upon the particular experiment). The fixed ring form of the trans isomer of tamoxifen is an antiestrogen, whereas the cis isomer is estrogenic. Fixed ring-trans-4-hydroxytamoxifen is a potent antiestrogen, and its cis isomer is a weak antiestrogen (IC50 congruent to 4 x 10(-8) to 2 x 10(-7) M). The fixed ring form of trans-metabolite E (tamoxifen without the dimethylaminoethane side chain) is only a weak partial estrogen agonist, whereas the fixed ring derivative of its cis isomer is a potent estrogen agonist (EC50 congruent to 4 x 10(-12) to 1 x 10(-11) M). These studies have determined the true biological activities of the hydroxylated derivatives of tamoxifen. This information will be valuable for the development of drug receptor models and will be particularly useful when the three-dimensional structure of the receptor complex is determined.