QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) All Versions of this Article: jpet.103.062505v1 309/3/1093    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zacharia, L. C. Articles by Jackson, E. K. Search for Related Content PubMed PubMed Citation Articles by Zacharia, L. C. Articles by Jackson, E. K.

ABSORPTION, DISTRIBUTION, METABOLISM, AND EXCRETION

2-Hydroxyestradiol Is a Prodrug of 2-Methoxyestradiol

Center for Clinical Pharmacology (L.C.Z., R.K.D., E.K.J.), Departments of Medicine and Pharmacology (E.K.J.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; PR Pharmaceuticals (C.A.P., K.M.H., S.D.A.), Fort Collins, Colorado; and Biologistic Services (R.M.F.), Boulder, Colorado

Received November 4, 2003; accepted February 6, 2004.

	Abstract

Top Abstract Materials and Methods Results Discussion References

 
Previous in vivo studies indicate that 2-hydroxyestradiol (2OHE) attenuates cardiovascular and renal diseases. In vitro studies suggest that the biological effects of 2OHE are mediated by 2-methoxyestradiol (2MEOE) after methylation of 2OHE by catechol-O-methyltransferase (COMT). This study tested the hypothesis that in vivo 2OHE is a prodrug of 2MEOE. We administered to male rats i.v. boluses of either 2OHE or 2MEOE and measured plasma levels of 2OHE and 2MEOE by gas chromatography-mass spectrometry at various time points after drug administration. After administration of 2OHE, plasma levels of 2OHE declined extremely rapidly [t_1/2(1) = 0.94 min and t_1/2(2) = 10.2 min] becoming undetectable after 45 min. Concomitant with the disappearance of 2OHE, 2MEOE occurred and then declined [t_1/2(1) = 7.9 min and t_1/2(2) = 24.9 min]. The peak concentration and total exposure (area under the curve) for 2OHE were much lower than for 2MEOE. 2OHE had a much higher plasma clearance (CL) and volume of distribution (V_d) compared with 2MEOE (2OHE: CL = 1215 ml min^-1 kg^-1 and V_d = 17,875 ml/kg; 2MEOE: CL = 50 ml min^-1 kg^-1 and V_d = 1760 ml/kg). After administration of 2MEOE, plasma levels of 2MEOE declined [t_1/2(1) = 2.5 min and t_1/2(2) = 20.2 min] with a plasma CL of 50 ml min^-1 kg^-1 and a V_d of 1500 ml/kg. We could not detect 2OHE in plasma from rats receiving 2MEOE. We conclude that the conversion of 2OHE to 2MEOE is so efficient that in terms of 2MEOE exposure, administration of 2OHE is bioequivalent to administration of 2MEOE itself.

Although the aforementioned in vivo studies were conducted with 2OHE, in point-of-fact 2OHE is readily oxidized and is therefore a poor candidate for drug development. 2-Methoxyestradiol (2MEOE), on the other hand, is less susceptible to oxidation, and in vitro evidence suggests that most of the cellular effects of 2OHE are mediated by 2MEOE, a metabolite of 2OHE that is devoid of estrogenic activity. In this regard, inhibition of catechol-O-methyltransferase (COMT), the enzyme that methylates 2OHE and converts it to 2MEOE, blocks the ability of 2OHE to inhibit growth of vascular smooth muscle cells (Dubey et al., 2000), cardiac fibroblasts (Dubey et al., 2002b), and renal mesangial cells (Dubey et al., 2002a). Moreover, 2OHE inhibits vascular smooth muscle cell growth in cells obtained from wild-type mice but not in cells cultured from COMT knockout mice (Zacharia et al., 2003b). In contrast to 2OHE, treatment of vascular smooth muscle cells with 2MEOE inhibits serum-induced growth of cells from both wild-type and COMT-knockout mice (Zacharia et al., 2003b).

We hypothesize that in vivo 2OHE is essentially a prodrug of 2MEOE and is converted so rapidly to 2MEOE as to be essentially bioequivalent with administration of 2MEOE. This hypothesis is supported indirectly by our recent findings that 2OHE is converted to 2MEOE very efficiently by the perfused rat kidney and heart (Zacharia et al., 2003a). The purpose of the present study was to directly test this hypothesis by carefully examining and comparing the pharmacokinetic behavior of both 2OHE and 2MEOE. The importance of testing this hypothesis is that if 2OHE is bioequivalent to the more stable metabolite 2MEOE, then 2MEOE would be a better drug candidate.

	Materials and Methods

Top Abstract Materials and Methods Results Discussion References

 
Animals. Adult male Sprague-Dawley rats (260-310 g) were acclimated for at least 5 days before use. Male rats were used to avoid endogenous 2OHE and 2MEOE that would be present in female rats. The rats were fed a laboratory animal feed and were provided tap water ad libitum. Lighting was on a standard 12-h on, 12-h off cycle. The humidity in the housing area during the study was 50% and the temperature was 68°F.

Drugs. 2OHE and 2MEOE were obtained from Steraloids (Newport, RI) and dissolved in polyethylene 200 at a concentration of 1 mg/ml.

Protocol. Rats (n = 84) were anesthetized with isoflurane and received a single i.v. injection of 0.5 mg/kg of either 2OHE (n = 42) or 2MEOE (n = 42). Blood samples (6 ml) were obtained at 1, 2, 5, 10, 15, 20, 30, 45, 60, 90, 120, 180, 240 and 360 min after dosing. Animals were anesthetized with isoflurane for blood sampling, and samples were obtained by cardiac stick before euthanasia. Ascorbic acid (final concentration 1 mM) was added to each sample to prevent oxidation of 2OHE and 2MEOE. Only a single blood sample was taken per rat, and three rats were used for each time point. After the blood samples were obtained, animals were euthanized with CO₂.

Assay for 2OHE and 2MEOE. We recently developed and validated a gas chromatography/mass spectrometry assay for 2OHE and 2MEOE in rat plasma (Zacharia et al., 2004), and this assay was used in the current study. Briefly, plasma samples were deprotonated using acetone, dried, reconstituted in acetonitrile, derivatized with pentafluorpropionic acid anhydride, and analyzed by negative chemical ionization on a ThermoQuest Finnigan Trace gas chromatograph/mass spectrometer. The metabolites 2OHE and 2MEOE were assayed simultaneously, and levels were determined from a standard curve prepared in rat plasma. The detection limit for both metabolites was 0.25 pg/µl. Interassay coefficients of variation were for 2OHE 7.1, 6.6, and 3.4% and for 2MEOE 16.7, 16.6, and 12% for the low- (0.375pg/µl), medium- (1.875 pg/µl), and high (4.375 pg/µl)-quality control samples, respectively. Intra-assay coefficients of variation were for 2OHE 15.6, 26.2, and 25.6% and for 2MEOE 16.5, 11.78, and 11.23% for the low-, medium-, and high-quality control samples, respectively.

Statistical Methods. Standard pharmacokinetic parameters for 2OHE and 2MEOE were determined from mean plasma concentration versus time data. Plots of mean plasma concentration versus time data include ± standard deviation for each mean plasma concentration data point. Because of the rapid and extensive metabolic conversion of 2OHE to 2MEOE observed in this study, pharmacokinetic analysis was also applied to the 2MEOE plasma data after administration of 2OHE. Areas under the concentration versus time curve (AUC) were calculated from time 0 to the last measurable time point (360 min). Plasma concentration data were fit to polyexponential equations, using a nonlinear, least-squares method (RSTRIP; MicroMath Inc., Salt lake City, UT) to determine the apparent half-lives (t_1/2) of each phase, and time 0 plasma concentrations (C₀).

	Results

Top Abstract Materials and Methods Results Discussion References

 
Pharmacokinetic Analysis of 2MEOE after Bolus Dosing of 2MEOE. The pharmacokinetic parameters for 2MEOE calculated from a study using intravenous boluses of 2MEOE in male rats are shown in Table 1. After i.v. injection, 2MEOE exhibited a multiphasic serum versus time profile (Fig. 1). Peak plasma concentrations of >500 ng/ml were observed immediately after the injection (C_max = 584 ng/ml). Plasma levels initially fell rapidly [t_1/2(1) = 2.5 min], then more slowly [t_1/2(2) = 20.2 min] over the first 2 h. The initial concentration of 2MEOE achieved (C₀) was 751 ng/ml with an initial volume of distribution, V_c (volume of the central compartment), of 666 ml/kg. 2MEOE was rapidly eliminated over the next 2 h with concentrations of plasma falling nearly 500-fold in 360 min. Although the shape of the plasma concentration versus time curve prevented accurate determination of the terminal elimination rate, the AUC calculated from time 0 to 360 min is likely to be a close approximation to the total AUC due to the low levels observed at the last time point. Based on the AUC from 0 to 360 min, the clearance of 2MEOE was 50 ml min^-1 kg^-1. Assuming that the elimination half-life is that of the second phase observed in this study [t_1/2(2) = 20.2 min], then a volume of distribution (V_d; volume of distribution during elimination) of approximately 1500 ml/kg would be predicted during the elimination phase.

View larger version (18K): [in this window] [in a new window]   Fig. 1. Line graph illustrating the relationship between mean ± S.D. plasma levels of 2MEOE concentrations versus time after i.v. administration of 0.5 mg/kg 2-methoxyestradiol. The insert represents the fitted curve using a biexponential equation.

Pharmacokinetic Analysis of 2OHE after Bolus Dosing of 2OHE. The pharmacokinetic parameters of 2OHE after intravenous administration are shown in Table 1. After i.v. injection, 2OHE exhibited a biphasic serum versus time profile (Fig. 2). Plasma 2OHE concentrations peaked at approximately 100 ng/ml immediately after injection (C_max = 107 ng/ml). Plasma levels fell extremely rapidly [t_1/2(1) = 0.94 min] for the first few minutes, then more slowly, but still very rapidly [t_1/2(2) = 10.2 min] over the next half-hour. Plasma levels were not detectable at time points more than 45 min after dosing. The initial concentration of 2OHE, C₀, was 216 ng/ml with an initial volume of distribution, V_c, of 2315 ml/kg. The AUC from time 0 to 45 min is likely to be a close approximation to the total AUC due to the low levels observed at the last time point. Based on this AUC, the clearance of 2OHE was 1215 ml min^-1 kg^-1. Based on the observed terminal half-life in this study [t_1/2(2) = 10.2 min], 2OHE has a very large V_d of approximately 18,000 ml/kg.

View larger version (16K): [in this window] [in a new window]   Fig. 2. Line graph illustrating the relationship between mean ± S.D. plasma levels of 2OHE versus time after i.v. administration of 0.5 mg/kg 2-hydroxyestradiol. The inset represents the fitted curve using a biexponential equation.

Pharmacokinetic Analysis of 2MEOE after Bolus Doses of 2OHE. The pharmacokinetic parameters of the metabolite 2MEOE after 2OHE administration are shown in Table 1. After i.v. injection of 2OHE, plasma concentrations of the metabolite rose rapidly (C_max, 494 ng/ml at 2 min), then fell in a biexponential manner over the next 3 h (Fig. 3). Both the initial and terminal half-lives of 2MEOE [t_1/2(1) = 7.9 min and t_1/2(2) = 24.9 min, respectively] were longer than those observed for the parent 2OHE. The plasma concentration versus time profile of 2MEOE after 2OHE injection was nearly identical to that observed after injection of the 2MEOE itself at the same dose (Fig. 4). The AUCs of 2MEOE observed after 2OHE administration were nearly identical after administration of 2OHE or 2MEOE, with similar peak plasma levels and half-lives. The C₀ of 2MEOE achieved in this study was 495 ng/ml with a V_c of 1010 mg/kg. From the AUCs in plasma observed after 2OHE administration, the clearance of 2MEOE was approximated to be 50 ml min^-1 kg^-1. Based on the observed terminal half-life in this study [t_1/2(2) = 24.9 min], 2MEOE has a V_d of approximately 1760 ml/kg. Figure 5 shows the plasma concentration versus time relationships on the same graph for 2OHE and 2MEOE after administration of 2OHE.

View larger version (17K): [in this window] [in a new window]   Fig. 3. Line graph illustrating the relationship between mean ± S.D. plasma levels of 2MEOE versus time after i.v. administration of 0.5 mg/kg 2-hydroxyestradiol. The inset represents the fitted curve using a biexponential equation.

View larger version (16K): [in this window] [in a new window]   Fig. 4. Line graph illustrating the relationship between mean ± S.D. plasma levels of 2MEOE versus time after i.v. administration of either 2-methoxyestradiol or 2-hydroxyestradiol, each at 0.5 mg/kg.

View larger version (16K): [in this window] [in a new window]   Fig. 5. Line graphs illustrating the relationship between mean ± S.D. plasma levels of either 2OHE or 2MEOE after i.v. administration of 2-hydroxyestradiol (0.5 mg/kg).

	Discussion

Top Abstract Materials and Methods Results Discussion References

 
The hypothesis tested by this study is that 2OHE is a prodrug of 2MEOE. Our data demonstrate that administration of 2OHE is equivalent to the administration of 2MEOE with regard to the total exposure of the body to 2MEOE. Moreover, based on the clearances observed in this study, a constant rate infusion of 2OHE would result in steady-state concentrations of 2MEOE that are approximately 25-fold higher than steady-state concentrations of 2OHE. In vitro, 2MEOE is more potent than 2OHE with regard to inhibiting growth of vascular smooth muscle cells (Dubey et al., 2000), cardiac fibroblasts (Dubey et al., 2002b), and renal mesangial cells (Dubey et al., 2002a). Moreover, 2OHE has little estrogenic activity, and its in vitro effects are not blocked by estrogen receptor antagonist ICI 182,780 (Dubey et al., 2000). Because 2OHE is nearly quantitatively converted to 2MEOE, because constant rate infusions of 2OHE would produce steady-state levels of 2MEOE that are 25-fold higher than steady-state levels of 2OHE, and because the cellular effects of 2MEOE are more potent than 2OHE, together our findings indicate that 2OHE is a prodrug of 2MEOE. It is conceivable, however, that at extremely high infusion rates of 2OHE, steady-state concentrations of 2OHE may reach sufficiently high levels to have direct biological activity. Nonetheless, given the pharmacokinetic and pharmacodynamic profiles of 2OHE versus 2MEOE, it seems appropriate to call 2OHE a prodrug of 2MEOE.

The conclusion that administration of 2OHE is equivalent to the administration of 2MEOE with regard to the total exposure of the body to 2MEOE is based on the following considerations. The plasma concentration versus time profile of 2MEOE after i.v. injection of 2OHE is nearly identical to the profile after i.v. injection of the same dose of 2MEOE. Moreover, the AUC for 2MEOE after i.v. administration of 2OHE is very similar to the AUC after i.v. administration of the same dose of 2MEOE. Also, the peak plasma levels and half-lives of 2MEOE after i.v. administration of 2MEOE are similar to those observed after i.v. administration of the same dose of 2OHE. Thus, in terms of exposure to 2MEOE, 2OHE, and 2MEOE injections seem to be equivalent.

The high clearance of 2OHE (1215 ml min^-1 kg^-1) exceeds the rat's liver blood flow (approximately 55 ml min^-1 kg^-1), suggesting that 2OHE is subject to extensive extrahepatic metabolism to 2MEOE. Indeed the clearance of 2OHE even exceeds the rat's cardiac output (approximately 300 ml min^-1 kg^-1). This exceedingly high clearance of 2OHE is most consistent with the concept that 2OHE partitions rapidly and extensively into erythrocytes where it is quickly converted to 2MEOE by COMT. The high COMT content of erythrocytes (Männisto and Kaakkola, 1999) is supportive of this hypothesis. Based on the observed terminal half-life in this study (10.2 min), 2OHE has an extremely large volume of distribution (approximately 18,000 ml/kg). This finding indicates that 2OHE is extensively distributed to sites outside the plasma compartment (including blood cells). This high volume of distribution provides ample encounters with COMT to methylate 2OHE to 2MEOE.

The sample size per time point (three animals per time point) was adequate for the overall characterization of 2MEOE serum pharmacokinetics. The half-lives we report, from curve fits to mean serum data, are estimates whose values are clearly subject to variability observed within the sample population. The pharmacokinetic profile of 2MEOE was "multiphasic", and this is consistent with the most important characterization of the kinetic profile, i.e., 2MEOE disappears rapidly from serum after administration in a manner suggesting that both distributional and metabolic components are involved.

The pharmacokinetics of 2OHE and 2MEOE after 2OHE administration has been previously examined in humans using radioimmunoassay as the detection method (Kono et al., 1982). The current study used a highly sensitive and specific gas chromatographic-mass spectrometric assay and used an experimental design that allowed a comprehensive comparison of the pharmacokinetic profiles of 2OHE versus 2MEOE. Importantly, there were no major differences in the pharmacokinetic parameters in our studies in rats and versus the previous study in humans, indicating that the conclusions of the present study most likely hold for human beings as well.

The results of the present study have important implications. In this regard, endogenous estradiol can be hydroxylated by cytochrome P450s in the liver (Ball and Knuppen, 1978; Martucci and Fishman, 1993) and in nonhepatic tissues (Ball and Knuppen, 1978; Martucci and Fishman, 1993) to form 2OHE. The fact that administration of 2OHE behaves very similarly to administration of 2MEOE suggests that endogenously synthesized 2OHE is converted rapidly, locally, and mostly to 2MEOE. Rapid methylation of 2OHE to 2MEOE is consistent with the possibility that 2MEOE is an active endogenous compound.

Inasmuch as 2MEOE inhibits growth of vascular smooth muscle cells (Dubey et al., 2000), cardiac fibroblasts (Dubey et al., 2002b), renal mesangial cells (Dubey et al., 2002a), and cancer cells and is an antimitogenic agent, the present data suggest that metabolism of endogenous 2OHE to 2MEOE may importantly contribute to protection against cardiovascular/renal diseases and cancer. Any reduction in the efficacy of COMT-mediated methylation of 2OHE could lead to increased susceptibility to disease. In this regard, because catecholamines inhibit methylation of 2OHE (Zacharia et al., 2001), stress-induced activation of the sympathoadrenal axis may limit the protection afforded by this biochemical pathway. Also, the COMT gene has low, intermediate, and high efficiencies due to genetic polymorphisms (Boudikova et al., 1990), and therefore individuals may be protected differently by endogenous 2OHE depending on their genotype.

From the therapeutic perspective, because the administration of 2OHE is equivalent to administering 2MEOE, our data imply that the pharmacology of 2MEOE would be similar to that of 2OHE. This may be advantageous because 2OHE is less chemically stable (more readily oxidized) compared with 2MEOE and therefore 2MEOE may be more easily formulated as a drug. Indeed, we have successfully formulated 2MEOE in biodegradable microparticles for sustained release resulting in pharmacologically active plasma levels of 2MEOE in rats for up to 1 month after a single subcutaneous injection (work in progress). The potential use of 2MEOE is currently being evaluated in phase I and phase II clinical trials for the treatment of multiple types of cancer, including breast cancer, advanced refractory metastatic breast cancer, and hormone-refractory prostate cancer (Lakhani et al., 2003). In addition to being a potent anticarcinogenic agent, animal studies provide evidence that 2MEOE may effectively protect against proliferative disorders associated with cardiovascular disease, renal disease, and obesity (Tofovic et al., 2001, 2002).

In conclusion, the results of the present study strongly support the hypothesis that 2OHE is converted mostly to 2MEOE and that 2OHE is, for all practical purposes, a prodrug of 2MEOE.

	Footnotes

 
DOI: 10.1124/jpet.103.062505.

ABBREVIATIONS: 2OHE, 2-hydroxyestradiol; 2MEOE, 2-methoxyestradiol; COMT, catechol-O-methyltransferase; AUC, area under the curve; V_c, volume of the central compartment; V_d, volume of distribution; ICI 182,780, fulvestrant.

Address correspondence to: Dr. Edwin K. Jackson, 623 Scaife Hall, Center for Clinical Pharmacology, 3550 Terrace St., University of Pittsburgh School of Medicine, Pittsburgh, PA 15261. E-mail: edj{at}pitt.edu

	References

Top Abstract Materials and Methods Results Discussion References

 

Ball P and Knuppen R (1978) Formation of 2- and 4-hydroxyestrogens by brain, pituitary, and liver of the human fetus. J Clin Endocrinol Metab 47: 732-737.[Abstract/Free Full Text]

Ball P and Knuppen R (1990) Formation, metabolism, and physiologic importance of catecholestrogens. Am J Obstet Gynecol 163: 2163-2170.[Medline]

Boudikova B, Szumlanski C, Maidak B, and Weinshilboum R (1990) Human liver catechol-O-methyltransferase pharmacogenetics. Clin Pharmacol Ther 48: 381-389.[Medline]

Dubey RK, Gillespie DG, Keller PJ, Imthurn B, Zacharia LC, and Jackson EK (2002a) Role of methoxyestradiols in the growth inhibitory effects of estradiol on human glomerular mesangial cells. Hypertension 39: 418-424.[Abstract/Free Full Text]

Dubey RK, Gillespie DG, Zacharia LC, Rosselli M, Imthurn B, and Jackson EK (2002b) Methoxyestradiols mediate the antimitogenic effects of locally applied estradiol on cardiac fibroblast growth. Hypertension 39: 412-417.[Abstract/Free Full Text]

Dubey RK, Gillespie DG, Zacharia LC, Rosselli M, Korzekwa KR, Fingerle J, and Jackson EK (2000) Methoxyestradiols mediate the antimitogenic effects of estradiol on vascular smooth muscle cells via estrogen receptor-independent mechanisms. Biochem Biophys Res Commun 278: 27-33.[CrossRef][Medline]

Kono S, Merriam GR, Brandon DD, Loriaux DL, and Lipsett MB (1982) Radioimmunoassay and metabolism of the catechol estrogen 2-hydroxyestradiol. J Clin Endocrinol Metab 54: 150-154[Abstract/Free Full Text]

Lakhani NJ, Sarkar MA, Venitz J, and Figg WD (2003) 2-Methoxyestradiol, a promising anticancer agent. Pharmacotherapy 23: 165-172.[CrossRef][Medline]

Männistö PT and Kaakkola S (1999) Catechol-O-methylthransferase (COMT): biochemistry, molecular biology, pharmacology and clinical efficacy of the new selective COMT inhibitors. Pharmacol Rev 51: 593-628.[Abstract/Free Full Text]

Martucci CP and Fishman J (1993) P450 enzymes of estrogen metabolism. Pharmacol Ther 57: 237-257.[CrossRef][Medline]

Tofovic SP, Dubey R, Salah EM, and Jackson EK (2002) 2-Hydroxyestradiol attenuates renal disease in chronic puromycin aminonucleoside nephropathy. J Am Soc Nephrol 13: 2737-2747.[Abstract/Free Full Text]

Tofovic SP, Dubey RK, and Jackson EK (2001) 2-Hydroxyestradiol attenuates the development of obesity, the metabolic syndrome and vascular and renal dysfunction in obese ZSF1 rats. J Pharmacol Exp Ther 299: 973-977.[Abstract/Free Full Text]

Tofovic SP, Maddy H, and Jackson EK (2003a) Estradiol metabolites attenuate renal and cardiovascular injury induced by chronic angiotensin II administration. Hypertension (Abstract P52) 42: 414.

Tofovic SP, Maddy H, Salah E, Jackson EK, and Melhem M (2003b) Estradiol metabolites retard the progression of pulmonary hypertension - preclinical evidence for clinical development (Abstract P62). Hypertension 42: 416.

Zacharia LC, Dubey RK, and Jackson EK (2004) A gas chromatography mass spectrometry assay to measure estradiol, catecholestradiols and methoxyestradiols in plasma. Steroids, in press.

Zacharia LC, Dubey RK, Mi Z, and Jackson EK (2003a) Methylation of 2-hydroxyestradiol in isolated organs. Hypertension 42: 82-87.[Abstract/Free Full Text]

Zacharia LC, Gogos JA, Karayiorgou M, Jackson EK, Gilliespie DG, Barchiesi F, and Dubey RK (2003b) Methoxyestradiols mediate the antimitogenic effects of 17-estradiol: direct evidence from catechol-O-methyltransferase knockout mice. Circulation 108: 2974-2978.[Abstract/Free Full Text]

Zacharia LC, Jackson EK, Gillespie DG, and Dubey RK (2001) Catecholamines abrogate antimitogenic effects of 2-hydroxyestradiol on human aortic vascular smooth muscle cells. Arterioscler Thromb Vasc Biol 21: 1745-1750.[Abstract/Free Full Text]

This article has been cited by other articles:

				A. Parada-Bustamante, P. A Orihuela, M. Rios, P. A Navarrete-Gomez, C. A Cuevas, L. A Velasquez, M. J Villalon, and H. B Croxatto Catechol-O-Methyltransferase and Methoxyestradiols Participate in the Intraoviductal Nongenomic Pathway Through Which Estradiol Accelerates Egg Transport in Cycling Rats Biol Reprod, December 1, 2007; 77(6): 934 - 941. [Abstract] [Full Text] [PDF]

				C. M. Masi, L. C. Hawkley, J. D. Berry, and J. T. Cacioppo Estrogen Metabolites and Systolic Blood Pressure in a Population-Based Sample of Postmenopausal Women J. Clin. Endocrinol. Metab., March 1, 2006; 91(3): 1015 - 1020. [Abstract] [Full Text] [PDF]

				D. Desaulniers, G.-H. Xiao, K. Leingartner, I. Chu, B. Musicki, and B. K. Tsang Comparisons of Brain, Uterus, and Liver mRNA Expression for Cytochrome P450s, DNA Methyltransferase-1, and Catechol-O-Methyltransferase in Prepubertal Female Sprague-Dawley Rats Exposed to a Mixture of Aryl Hydrocarbon Receptor Agonists Toxicol. Sci., July 1, 2005; 86(1): 175 - 184. [Abstract] [Full Text] [PDF]

				D. Desaulniers, G. M. Cooke, K. Leingartner, K. Soumano, J. Cole, J. Yang, M. Wade, and A. Yagminas Effects of Postnatal Exposure to a Mixture of Polychlorinated Biphenyls, p,p'-dichlorodiphenyltrichloroethane, and p-p'-dichlorodiphenyldichloroethene in Prepubertal and Adult Female Sprague-Dawley Rats International Journal of Toxicology, March 1, 2005; 24(2): 111 - 127. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) All Versions of this Article: jpet.103.062505v1 309/3/1093    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zacharia, L. C. Articles by Jackson, E. K. Search for Related Content PubMed PubMed Citation Articles by Zacharia, L. C. Articles by Jackson, E. K.