Estrone-3-glucuronide Research Articles

Direct enzyme immunoassay of fecal estrone derivatives in dairy cows

ABSTRACTThe present study was undertaken to develop a novel, practical and simple procedure for enzyme‐linked immunosorbent assay of fecal estrone derivatives (estrone, estrone sulfate and estrone glucuronide) in dairy cows. Fecal solution, prepared by mixing feces with borate buffer, was applied directly to wells without extraction, and incubated with anti‐estrone antibody and horseradish peroxidase‐labeled estrone. Estrone sulfate was used as the standard. The sensitivity of the assay was estimated as 0.15 ng/mL (0.6 ng/g). The intra‐assay and inter‐assay coefficients of variation were 5.3–8.1% and 13.4–15.7%, respectively. The recovery rate was 78–102%. Only 4 h were needed to complete an assay to measure fecal estrone derivative concentrations. A significant positive correlation was established between plasma estrone sulfate concentrations and fecal estrone sulfate equivalent concentrations. When fecal estrone sulfate equivalent concentrations were measured in pregnant dairy cows, a gradual increase from day 150 of pregnancy, and subsequent drastic increases from day 240 to calving date were observed. These results suggest that the direct enzyme immunoassay procedure developed in the present study is a practical and reliable method for measuring fecal estrone derivative concentrations.

Sequential classification of endocrine stages during reproductive aging in women: the FREEDOM study*

Reproductive aging involves complex endocrine changes affecting women's fertility, health, and well-being; however, understanding of the specific changes involved is limited by the lack of detailed quantitative studies. We undertook a thorough study with the aim of characterizing the different endocrine stages involved in female reproductive aging. FREEDOM is a cohort study designed to determine the endocrine changes during reproductive aging in women. Here, we ascertained the different endocrine patterns in a representative population and developed a staging system. In this study, 112 women aged 30 to 58 years collected daily urine samples over a 6- to 18-month period and recorded their menstrual periods. A total of 36,786 samples were analyzed for follicle-stimulating hormone (FSH), luteinizing hormone, estrone 3-glucuronide, and pregnanediol 3-glucuronide. A classification of five sequential endocrine stages of reproductive aging was developed: stage 1, regular menstrual cycles with mean initial (day 1-5) FSH less than 5 IU/L; stage 2, regular cycles with FSH greater than 5 IU/L; stage 3, menstrual irregularity (with the appearance of "delayed-response cycles"); stage 4, acyclical ovarian activity with no evidence of ovulation and luteinization; and stage 5, ovarian quiescence and persistently raised gonadotropins. Distinct hormonal characteristics during the follicular and luteal phase were noted at each stage. This classification provides a detailed insight into the endocrinology of reproductive aging in women that could be useful for both clinical guidance and personal health care.

Origins and consequences of the elongation of the human menstrual cycle during the menopausal transition: the FREEDOM Study.

The menopausal transition is characterized by the appearance of elongated cycles, which become longer and more frequent as menopause approaches. Several endocrine abnormalities have been attributed to these cycles; however, no quantitative studies of their causes and consequences exist to date. This study is based on sequential daily urinary concentrations of FSH, LH, estrone 3-glucuronide (E1G), and pregnanediol 3-glucuronide (PdG) from 34 women with perimenopausal menstrual irregularity (total of 289 cycles). The timing of ovarian response was determined as the day of E1G take-off (ETO). Other parameters measured were the mean FSH concentration before ETO (FSH(ETO)) and the midluteal levels of PdG, E1G, and LH. There was a strong parallelism between ETO and cycle length variability. FSH(ETO) levels increased gradually with ETO. Both ETO and FSH(ETO) were inversely related to luteal PdG and directly related to E1G. PdG and LH levels were inversely related. All comparisons were highly significant (P < 0.0001). We conclude that delayed ovarian response underlies the elongation of the menstrual cycle in the menopausal transition, which is likely to be caused by a temporary lack of ovarian responsiveness to FSH. A progressive decline in luteal PdG with increased E1G occurs in association with these trends.

Relationship between follicle-stimulating hormone levels at the beginning of the human menstrual cycle, length of the follicular phase and excreted estrogens: the FREEDOM study.

Although reproductive aging has been separately related to elevated FSH and shorter follicular phase (FP), the direct association between both parameters has not been investigated. Also, the exact effects of increased FSH on estrogen production are yet to be established.A large database of daily urinary concentrations of FSH, LH, and estrone 3-glucuronide (E1G) from 37 regularly menstruating women (median 11 cycles per patient) was used. Initial FSH levels (iFSH) were estimated as the mean value of d 1-5. The day of E1G take-off (ETO) was determined by an algorithm, and accordingly, the FP was divided into early (d 1 to ETO) and late (ETO+1 to LH peak). FP maximum and integrated E1G were calculated. Subjects were distributed according to their mean iFSH into three categories (</=5, >5 to 10, and >10 IU/liter). There was a gradual decrease in FP length with increasing category (15.2 +/- 3.8, 14.1 +/- 3.6, and 13 +/- 2.6 d, respectively; P < 0.0001). A similar effect occurred in early FP (7.5 +/- 4, 6.4 +/- 3.7, and 5.4 +/- 2.7; P < 0.0001); in contrast, late FP was unaffected (7.7 +/- 2.1, 7.7 +/- 2.1, and 7.6 +/- 2.4; P = 0.86). No consistent increase in E1G was found with advancing iFSH category; however, women with mean initial LH higher than 6 IU/liter had significantly elevated maximum (P < 0.0001) and integrated (P = 0.002) E1G.FP length decreases in parallel with increasing iFSH, with a selective effect on the early FP. Increased FSH does not affect E1G; however, elevated initial LH level was related to higher E1G.

Effect of emergency contraception with levonorgestrel or mifepristone on ovarian function

The mechanism of action of levonorgestrel (LNG) and mifepristone (MIF) in emergency contraception (EC), is still not fully known. The purpose of this study was to evaluate the effect of preovulatory treatment with LNG and MIF on luteal function in more detail. Two days prior to ovulation (day −2; assessed by ultrasound), we administered LNG (0.75 mg twice, 12 h apart) or MIF (10 mg, single dose) to seven women in different cycles. Follicle development was followed by ultrasound. Urinary estrone glucuronide (E1), pregnanediol glucuronide (P4) and luteinizing hormone (LH) were analyzed by enzyme immunoassays daily starting with day −2 for the rest of the menstrual cycle, along with urinary creatinine (C). The treatment caused either a delay or an inhibition of the LH peak in all subjects. A significant delay in P4 levels and an initial suppression of E1 levels were also noted. The development of the leading follicle was either arrested or continued without signs of rupture. This study indicates that, when used for EC, LNG or MIF administered prior to ovulation acts through an impaired ovulatory process and luteal function.

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

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.

Urinary-based ovulation and pregnancy: point-of-care testing.

To review the literature concerning ovulation prediction devices and pregnancy detection tests for home use. Articles were identified through searches of the MEDLINE (1966-May 2003), EMBASE (1980-May 2003), and International Pharmaceutical Abstracts (1970-May 2003) databases using the key words ovulation, ovulation detection, pregnancy test, diagnostic reagent kit, and diagnostic test. Additional references were located through review of the bibliographies of the articles found in the literature search. Searches were not limited by time restriction, language, or use of human or animal subjects. Review articles, textbook chapters, and experimental and observational studies on home use ovulation and pregnancy tests were selected. Luteinizing hormone (LH)-based ovulation tests have demonstrated accurate and superior ovulation detection when compared to basal body temperature charting, calendar calculation, salivary ferning, or observation of vaginal or cervical discharge changes. Systems using LH and estrone-3-glucuronide (E3G) have also demonstrated accurate detection of the fertile period. Literature evaluating home use of pregnancy tests has demonstrated accurate use by lay persons. Urinary-based ovulation prediction and pregnancy detection tests available for use by nonprofessionals enable women and couples to take an active role in the family planning process. Numerous products are available at reasonable costs to the consumer.

Comparison between creatinine and pregnanediol adjustments in the retrospective analysis of urinary hormone profiles during the human menstrual cycle

Measurement of reproductive hormones in urine is a practical way of obtaining large amounts of information; however, there is still controversy on how to overcome problems derived from volume fluctuations between samples. Creatinine adjustment is a widely accepted solution, however, it introduces an extra cost, and large studies involving multiple sequential determinations would benefit from more economical solutions. We determined the value of creatinine adjustment, and compared it with a mathematical method that uses the smoothed profile of pregnanediol (PdG) as a reference to adjust other hormonal markers. To do this, we investigated the effects on three major urinary reproductive hormonal markers (luteinizing hormone (LH), estrone 3-glucuronide (E1G) and PdG) in 17 complete menstrual cycles. Detection of the day of LH peak did not differ between raw and adjusted data. Creatinine adjustment reduced variation in pre-ovulatory E1G levels between individuals, though the effect was negligible within individuals. No significant differences were found regarding post-ovulatory PdG rise. Although creatinine adjustment significantly reduces variability, producing smoother profiles, an equivalent degree of smoothness is obtained using the PdG adjustment. We conclude that under the current technology, for the retrospective study of urinary hormonal profiles in the human menstrual cycle, PdG adjustment is a valid alternative to creatinine.

Hormonal monitoring of ovarian activity using the Ovarian Monitor, Part I. Validation of home and laboratory results obtained during ovulatory cycles by comparison with radioimmunoassay

A study was conducted to determine the accuracy and reliability of the Home Ovarian Monitor for measuring estrone glucuronide (E1G) and pregnanediol glucuronide (PdG) during ovulatory cycles as a means of monitoring ovarian activity. Approximately 60 ovulating women in three centres collected timed specimens of urine (3 h or more) for a total of six cycles each. The women measured the E1G and PdG excretion per 24 h in their urine specimens using the Monitor. A local laboratory using the Monitor also measured the excretion. Urine specimens from 18 to 19 cycles were sent frozen to the WHO Reference Laboratory in London where they were analysed for E1G and PdG by the Monitor and by radioimmunoassay (RIA). The correlation coefficients between the Monitor and radioimmunoassay results obtained in London were better than 0.84 in 80% of the cycles. A urine bias caused the Monitor E1G results to be higher than those obtained by radioimmunoassay but the daily patterns were the same. In 50% of the cycles, this bias caused a delay of up to 3 days in identifying the beginning of the E1G rise compared with radioimmunoassay. Timing of the preovulatory E1G peak and the postovulatory PdG rise agreed within the experimental errors of the two systems. The study confirmed that women using the Monitor at home obtained results that were as accurate as those obtained by laboratory procedures. Careful supervision was required to maintain laboratory levels of quality control and interpretation of results.

Lysozyme conjugate immune complex formation and the effects on substrate hydrolysis

The defined estrone glucuronide–lysozyme conjugate E3, that is acylated solely at K33, was used as a probe for the steric requirements of the active site cleft of chicken type lysozymes. When the immune complex was formed with an anti-estrone glucuronide antiserum, the rate of lysis of the E3 conjugate with the large bacterial substrate Micrococcus lysodeikticus was inhibited by over 90%. However, when the small hexamer of N-acetyl glucosamine was used as the substrate, the rate of hydrolysis by the immune complex was accelerated by 350% compared with the control rate. Thus, inhibition by the anti-estrone glucuronide cannot be caused simply by steric occlusion of the active site. Other factor(s) in the immune complex activate the hydrolysis reaction, most likely by favouring the conformations that lead to the transition state.

Use of Defined Estrone Glucuronide–Hen Egg White Lysozyme Conjugates as Signal Generators in Homogeneous Enzyme Immunoassays for Urinary Estrone Glucuronide

Three structurally characterized estrone glucuronide–lysozyme conjugates, E1 (a 60:40 mixture acylated at K3 and K97), E3 (acylated at K33), and E5 (acylated at both K33 and K97) were isolated and purified using a combination of cation-exchange chromatography on S-sepaharose in 7 M urea and hydrophobic interaction chromatography on butyl sepharose. Urea was essential to separate the conjugates into six chromatographically homogeneous fractions. In the absence of urea, complex mixtures of lysozyme and the six conjugate fractions were always encountered. The E1, E3, and E5 conjugates were highly inhibited by a sheep polyclonal anti-estrone glucuronide antibody only after the hydrophobic interaction chromatography step. The high level of inhibition enabled all three conjugates to be utilized as signal generators in homogenous enzyme immunoassays for urinary estrone glucuronide. Despite the apparently higher affinity of E3 for the antibody, both E1 and E3 gave standard curves that were indistinguishable provided that 1.7-fold more antiserum was used for E1. Both E1 and E3 yielded menstrual cycle urinary data that agreed with that provided by the Ovarian Monitor pre-coated assay tubes. Although, the menstrual cycle pattern was similar for the three signal generators, the E1G excretion rates yielded by E5 as the signal generator were only 60% of the reference values. Despite structural differences, there was no advantage gained in separating E1 and E3, but higher substituted conjugates such as E5 need removal for best assay performance.

Endocrine monitoring and its application to the management of the giant panda

AbstractUrinary estrogens (n=10) and progestins (n=4) were monitored in a total of 10 giant panda females. Estrogens were evaluated with two different immunoassays during the estrous period. The two different methodologies gave similar hormonal profiles, but different quantitative results due to differences in the crossreactivity of the different assay systems. High‐pressure liquid chromatography (HPLC) analysis of peak estrogen urine revealed that estrone sulfate was the major component, and estrone glucuronide was a minor component (97:3). A comparison of days of insemination in females that conceived and delivered offspring showed a correlation to insemination on days 1 and 2 post‐estrogen peak. An analysis of urinary progestins revealed that they were elevated over baseline concentrations following the estrogen surge during estrus (P&lt;0.0004). Zoo Biol 22:389–400, 2003. © 2003 Wiley‐Liss, Inc.

Urinary reproductive hormone level differences between African American and Caucasian women of reproductive age

Objective: To compare urinary levels of reproductive hormones in African American and Caucasian women. Design: Cross-sectional study. Setting: Ten United States Air Force (USAF) bases. Patient(s): African American (n = 33) and Caucasian (n = 65) women of reproductive age from a larger study of USAF women (n = 170). Intervention(s): None. Main Outcome Measure(s): Urinary endocrine end points: follicular luteinizing hormone (LH), preovulatory LH, level of LH surge peak, early follicular follicle stimulating hormone (FSH), follicular LH:FSH ratio, midluteal FSH, FSH rise before menses, early follicular estrone 3-glucuronide (E 13G), midfollicular E 13G, periovulatory E 13G peak, midluteal E 13G, early follicular pregnanediol 3-glucuronide (Pd3G), follicular Pd3G, rate of periovulatory Pd3G increase, E 13G:Pd3G on the day of luteal transition, slope of E 13G:Pd3G, and midluteal Pd3G. Result(s): Relative to Caucasians, African American women had significantly lower follicular phase LH:FSH ratios (mean ± SD: 0.7 ± 0.4 vs. 1.0 ± 0.6), lower follicular phase Pd3G levels (1.0 ± 0.5 vs. 1.2 ± 0.8 μg/mg creatinine), and lower rates of periovulatory Pd3G increase (0.5 ± 0.7 vs. 1.0 ± 1.2 μg/mg creatinine). Conclusion(s): Findings of this analysis should be considered preliminary evidence of racial differences in hormone levels. Future studies are needed to determine whether these differences have clinical significance.

Mean versus individual hormonal profiles in the menstrual cycle

Objective: To evaluate hormonal profiles of normal menstrual cycles. Design: Prospective, descriptive study of a case series. Setting: University-based natural family planning center. Patient(s): Twenty-five natural family planning users for three or more cycles (n = 78). These women were healthy, contraception-free, parous, with regular ovulatory cycles. Intervention(s): Immunoassays for estrone glucuronide, LH, and pregnanediol glucuronide were done in daily timed and measured samples of early morning urine. Main Outcome Measure(s): Estrone glucuronide, LH, and pregnanediol glucuronide levels were measured during the menstrual cycle. Result(s): All cycles showed an ovulatory pattern configuring classic hormonal mean curves. Most (77%) differed from the mean curve pattern. All had estrone glucuronide peaks, LH peaks, and pregnanediol glucuronide increases. Estrone glucuronide and LH peaks were not always clear; some lasted more than 1 day (long peak: estrone glucuronide 19%, LH 9%) or fluctuated (double peak: estrone glucuronide 4%, LH 6%; small LH peak: 19%). There were also prepeak estrone glucuronide surges, and pre- and postpeak LH surges. Pregnanediol glucuronide increased more clearly (6% fluctuated 1 day). Some women had repeated cycles with long estrone glucuronide peaks (16%) and fluctuations in LH surge (44%). Conclusion(s): Normal menstrual cycle hormonal profiles generally differ from mean curves, which are usually considered standard.

Evidence of reproductive endocrine effects in women with occupational fuel and solvent exposures.

Hydrocarbons (HCs) found in fuels and solvents are ubiquitous in the environment, yet we know little about their effects on the endocrine system. The objective of this study was to assess the potential reproductive endocrine effects of low-dose HCs encountered by female U.S. Air Force personnel with fuel (primarily JP-8 jet fuel) and solvent exposures (n = 63). We estimated the internal dose of HCs in fuels and solvents by measuring their levels in exhaled breath, including the sum of aliphatic HCs (C6H14-C16H34) and the sum of aromatic HCs (benzene, ethylbenzene, toluene, and m,p,o-xylenes). Adverse outcome measures included urinary endocrine markers that have been associated with nonconceptive (vs. conceptive) menstrual cycles in ovulatory women: lower preovulatory luteinizing hormone (LH) and mid-luteal phase pregnanediol 3-glucuronide (Pd3G) and estrone 3-glucuronide, and higher follicle phase Pd3G. We also obtained reproductive and exposure information from baseline questionnaires and daily diaries. Toluene was the most frequently found analyte in the breath, with values up to 52.0 ppb, and benzene breath levels were up to 97.5 ppb. Regression analysis revealed that preovulatory LH levels were significantly lower (p = 0.007) among women whose total aliphatic HC levels were above the median. The relationship between elevated aliphatic HC exposure and lowered preovulatory LH levels in the present study suggests that compounds in fuels and some solvents may act as reproductive endocrine disruptors. Confirmation of these findings is needed, not only to determine if fuel and solvent exposure may impact other LH-dependent physiologic functions but also to examine effects of fuels and solvents on conception.

IMPROVED PERFORMANCE OF ELISAs FOR FERTILITY ASSESSMENT USING COMMON REAGENTS AND ASSAY PROTOCOL AS EVIDENCE FROM QUALITY CONTROL STUDIES

ABSTRACT At our Institute, a panel of reproductive hormones, viz., estrone glucuronide (E1G), pregnanediol glucuronide (PdG), luteinising hormone (LH), and follicle stimulating hormone (FSH) are estimated by ELISA for the assessment of fertility from a single urine sample collected from a subject. In order to make the estimates less cumbersome, the selection and mode of presentation of immunoreagents of the assay were modified in such a way that, either on reconstitution or single dilution, would result in ready-to-use reagents in the assay. Retrospective analysis on the performance of these ELISAs with uniform protocols (n = 86) was compared with assays having individual assay protocols (n = 116). The performance of the assay, based on the standard curve characteristics and quality control pools, was better and the rate of acceptance of these assays improved from 87.9 to 97.6%. The simplification of assay protocols, thus, had better impact on the quality and reproducibility of immunoassay of the four analytes.

An electro-active system of immuno-assay (EASI assay) utilising self assembled monolayer modified electrodes

Most immunoassays currently rely on optical methods for signal generation e.g. in ELISA and rapid assay formats. It has become apparent as in the Glucose sensor market that there is a need for simple direct electrical immuno-sensors. We have investigated the novel use of organic conducting monolayers used as a direct electrochemical detection support for an immuno-reaction. It was found that antibodies raised to a carbazole dimer monolayer could increase the charge movement across that monolayer surface. Antibody fragments were taken from a specific anti-carbazole antibody fragment library and combined with an antibody fragment directed to the hormone estrone 3 glucuronide (E3G), the target antigen to form a bispecific antibody fragment. The device utilised these specific antibody fragments and incorporated them on the top plate of a capillary fill format as the immuno-assay components. The immuno-reaction utilised a competition assay. Free E3G analyte in the sample displaced the bispecific antibody fragment from the immuno-surface leaving it free to bind the carbazole monolayer surface. There the binding was detected using amperometric or coulometric methods. By combining all there element it was possible to develop a sensitive immuno-assay that could detect E3G in a reproducible calibrated fashion down to 10 ng/ml.

Assessment of Clearplan Fertility Monitor for monitoring donor insemination patients with and without clomiphene treatment.

Objective: The Clearplan Fertility Monitor (CFM) has been developed to record ‘high’ fertility from a urine dipstick when significant estrone glucuronide (EG) levels are present and ‘peak’ fertility when the luteinising hormone (LH) surge occurs. The objectives of the study were to demonstrate that the CFM could be used by patients attending a donor insemination (DI) clinic and by patients requiring clomiphene treatment.

An effective, economic way of monitoring menstrual cycle hormones in at risk female athletes.

Female athletes, in response to intensive training, competition stress and a lean, athletic physique, are at increased risk of altered hypothalamic-pituitary ovarian (HPO) axis function associated with menstrual cycle disturbance and reduced secretion of the ovarian hormones estrogen and progesterone. Because there is evidence suggesting possible detrimental effects on skeletal health associated with deficiencies in these hormones, a suitable means to asses ovarian hormone concentrations in at risk athletes is needed. The aim of this study was to evaluate a simple, economical means to monitor the ovarian hormone production in athletes, in the setting of intensive training. Subjects comprised 14 adolescent rowers, 12 lightweight rowers, and two groups of 10 matched control subjects. Ovarian function was monitored during the competition season by estimation of urinary excretion of estrone glucuronide (E1G) and pregnanediol glucuronide (PdG), enabling the menstrual cycles to be classified as ovulatory or anovulatory. Results indicated 35% and 75% of schoolgirl and lightweight rowers had anovulatory menstrual cycles, respectively. These findings were highlighted by significantly lower excretion of E1G and PdG during phases of intensive training in both the lightweight and schoolgirl rowers, compared with the control subjects. It was concluded that the urinary E1G and PdG assays were an effective means to assess the influence of intense training on ovarian hormone concentrations in at risk athletes. It is recommended that this technique be applied more widely as a means of early detection of athletes with low estrogen and progesterone levels, in an attempt to avoid detrimental influences on skeletal health.

Inhibition of deoxyglucose uptake in MCF-7 breast cancer cells by 2-methoxyestrone and 2-methoxyestrone-3- O-sulfamate

Most cancer cells are dependent on glucose uptake to fulfil their energy requirements. In the present investigation we have examined the ability of 2-methoxyestrone (2-MeOE1), 2-methoxyestradiol (2-MeOE2), 2-methoxyestrone-3- O-sulfamate (2-MeOEMATE), and a number of related compounds, to inhibit 2-deoxy- d-[1- 3H]-glucose uptake in MCF-7 breast cancer cells. Glucose uptake was shown to be linear with respect to cell number and time over a 5–35min period. 2-MeOE2, 2-MeOE1 and 2-MeOEMATE inhibited glucose uptake by 25–49% at 10 μM. 2-Hydroxyestradiol and estrone sulfate had little effect on glucose uptake, whereas estrone glucuronide inhibited uptake by 29%. There is evidence that 2-methoxyestrogens may exert an anti-mitotic effect on cells by stabilizing microtubules in a similar manner to that of paclitaxel. We therefore examined the effect of exposing cells to 2-MeOEMATE or paclitaxel for 24 h on basal or insulin stimulated glucose uptake. Using these conditions, 2-MeOEMATE and paclitaxel inhibited basal glucose uptake by 50 and 22%, respectively, and insulin stimulated uptake by 36 and 51%, respectively. The development of drugs that can inhibit glucose uptake could have therapeutic potential for the treatment of breast cancer.