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Kyung-Hoon Lee

Publications and source records attributed to Kyung-Hoon Lee.

At least 19 recordsLinked to original sources
PubMed2006

Angiotensin II type 1 receptor 1166A/C polymorphism in association with blood pressure response to exogenous angiotensin II.

BACKGROUND: The angiotensin II type 1 receptor (AT1R) 1166A/C polymorphism is reported to be implicated in cardiovascular diseases. The association between the 1166A/C polymorphism and diastolic blood pressure (DBP) changes in response to exogenous angiotensin II and valsartan was evaluated by pharmacokinetic and pharmacodynamic modeling. METHODS: Thirteen normotensive, healthy adults (six with the 1166A/A polymorphism and seven with 1166A/C) were enrolled in this clinical study. Angiotensin II was infused continuously over a 2-min period at four different rates (from 5 ng/kg/min and increased by 5 ng/kg/min) at 0 (before valsartan dosing), 2, 4, 8, 12, and 24 h after a single oral dose of valsartan (40 mg). BP was measured serially before and at the end of each rate of angiotensin II infusion. Plasma concentration-time profiles of valsartan were established over a 24-h period. We analyzed data using NONMEM and studied the relationship between the AT1R 1166A/C genotypes and BP responses. RESULTS: Plasma valsartan concentrations and DBP data best fitted into a two-compartment linear model and E(max) model (E(max) with baseline for angiotensin II and inhibitory E(max) for valsartan), respectively. The ED50 for angiotensin II in the subjects with 1166A/C [95% confidence interval (CI): 4.30 approximately 14.02 ng/kg/min] was significantly lower than in those with 1166A/A (95% CI: 14.23 approximately 28.77 ng/kg/min), while the E(max) for angiotensin II and EC50 for valsartan was similar in both genotype groups. CONCLUSIONS: These results suggest that exogenous human angiotensin II increases the BP more potently in subjects with 1166A/C than in those with 1166A/A.

Adult↗
PubMed2006

SP600125, a selective JNK inhibitor, aggravates hepatic ischemia-reperfusion injury.

c-Jun N-terminal kinase (JNK) is activated during hepatic reperfusion, and JNK inhibitors are known to protect other major organs from ischemia-reperfusion (I/R) injury. We attempted to determine the effect of SP600125, a JNK inhibitor, on hepatic I/R injury using a partial ischemia model in mice. Compared to a vehicle-treated group, the SP600125- treated group showed a greater increase in serum ALT levels 24 h after reperfusion with more severe parenchymal destruction and leukocyte infiltration. Similarly, tissue myeloperoxidase and malondialdehyde levels were higher in the SP600125-treated group, and chemokine expression was also higher in the SP600125-treated group. These data, which are contradictory to previous results, indicate that JNK inhibition by SP600125 may be harmful in hepatic I/R injury. Therefore, care must be taken when investigating the therapeutic use of JNK inhibitors in hepatic I/R injury, especially in the context of the effects of JNK inhibition on inflammatory infiltration.

Animals↗
PubMed2006

DA-9601, Artemisia asiatica herbal extract, ameliorates airway inflammation of allergic asthma in mice.

We previously reported that DA-9601, ethanol herbal extract of Artemisia asiatica, inhibited histamine and leukotriene releases in guinea pig lung mast cells activated with specific antigen/antibody reaction. This study aimed to evaluate the inhibitory effect of DA-9601 on the OVA-induced airway inflammation in allergic asthma mouse model. BALB/c mice were sensitized and challenged with OVA. DA-9601 was administered orally 1 h before every local OVA-challenge. OVA-specific serum IgE was measured by ELISA, recruitment of inflammatory cells in BAL fluids and lung tissues by Diff-Quik and H&E staining, respectively, the expressions of CD40, CD40L and VCAM-1 by immunohistochemistry, goblet cell hyperplasia by PAS staining, activities of MMPs by gelatin zymography, expressions of mRNA and proteins of cytokines by RT-PCR and ELISA, activities of MAP kinases by western blot, and activity of NF-KappaB by EMSA. DA-9601 reduced IgE level, recruitment of inflammatory cells into the BAL fluid and lung tissues, expressions of CD40, CD40L and VCAM-1 molecules, goblet cell hyperplasia, MMPs activity, expressions of mRNA and productions of various cytokines, activities of MAP kinases and NK-KappaB increased from OVA-challenged mice. These data suggest that DA-9601 may be developed as a clinical therapeutic agent in allergic diseases due to suppressing the airway allergic inflammation via regulation of various cellular molecules expressed by MAP kinases/NF-KappaB pathway.

Administration, Oral↗
PubMed2006

Akt phosphorylation is essential for nuclear translocation and retention in NGF-stimulated PC12 cells.

Nerve growth factor (NGF) elicits Akt translocation into the nucleus, where it phosphorylates nuclear targets. Here, we describe that Akt phosphorylation can promote the nuclear translocation of Akt and is necessary for its nuclear retention. Overexpression of Akt-K179A, T308A, S473A-mutant failed to show either nuclear translocation or nuclear Akt phosphorylation, whereas expression of wild-type counterpart elicited profound Akt phosphorylation and induced nuclear translocation under NGF stimulation. Employing the PI3K inhibitor and a variety of mutants PI3K, we showed that nuclear translocation of Akt was mediated by activation of PI3K, and Akt phosphorylation status in the nucleus required PI3K activity. Thus the activity of PI3K might contribute to the nuclear translocation of Akt, and that Akt phosphorylation is essential for its nuclear retention under NGF stimulation conditions.

Active Transport, Cell Nucleus↗
PubMed2006

Optimization of a dilution method for human expanded blastocysts vitrified using EM grids after artificial shrinkage.

PURPOSE: To verify a more effective dilution method that can be applied to human expanded blastocysts that are vitrified after artificial shrinkage. METHODS: Surplus expanded blastocysts that remained after embryo transfer (ET) in in vitro fertilization (IVF) cycles, were cryopreserved. The blastocysts were vitrified on EM grids following artificial shrinkage. After thawing the blastocysts, cryoprotectants were diluted using either a 6- or 2-step method. We examined the survival rate and clinical outcome of blastocysts of 151 patients in our ET program after thawing. RESULTS: The survival rate of blastocysts that were thawed using a 2-step method (91.6%, 239/261) was comparable with that of the 6-step method (89%, 186/209). The clinical pregnancy rate (45.9%, 39/85) and implantation rate (24.1%, 53/220) were slightly higher in the 2-step method than in the 6-step method (40.9%, 27/66; 19.4%, 33/170). CONCLUSIONS: Our data indicate that the 2-step dilution method could be a simpler and more effective protocol for human expanded blastocysts that are vitrified using EM-grid following artificial shrinkage.

Blastocyst↗
PubMed2006

Modulating protein structure with fluorous amino acids: increased stability and native-like structure conferred on a 4-helix bundle protein by hexafluoroleucine.

There has recently been much interest in exploiting the unusual properties associated with fluorocarbons to modulate the physicochemical properties of proteins. Here we present a detailed investigation into the effect on structure and stability of systematically repacking the hydrophobic core of a model protein with the extensively fluorinated (fluorous) amino acid l-5,5,5,5',5',5'-hexafluoroleucine (hFLeu). The starting point was a 27-residue peptide, alpha(4)-H, that adopts an antiparallel 4-alpha-helix bundle structure, and in which the hydrophobic core comprises six layers of leucine residues introduced at the "a" and "d" positions of the canonical heptad repeat. A series of peptides were synthesized in which the central two (alpha(4)-F(2))(,) four (alpha(4)-F(4)), or all six layers (alpha(4)-F(6)) of the core were substituted hFLeu. The free energy of unfolding increases by 0.3 (kcal/mol)/hFLeu on repacking the central two layers and by an additional 0.12 (kcal/mol)/hFLeu on repacking additional layers, so that alpha(4)-F(6) is approximately 25% more stable than the nonfluorinated protein alpha(4)-H. One-dimensional proton, two-dimensional (1)H-(15)N HSQC, and (19)F NMR spectroscopies were used to examine the effect of fluorination on the conformational dynamics of the peptide. Unexpectedly, increasing the degree of fluorination also appears to result in peptides that possess a more structured backbone and less fluid hydrophobic core. The latter only occurs in alpha(4)-F(4) and alpha(4)-F(6), suggesting that crowding of the hFLeu residues may restrict the amplitude and/or time scales for rotation of the side chains.

Amino Acid Sequence↗
PubMed2006

Effect of additives on the viability of bifidobacteria loaded in alginate poly-l-lysine microparticles during the freeze-drying process.

Bifidobacteria-loaded alginate poly-l-lysine microparticles (bap microparticles) were prepared using an air atomization method and then freeze-dried. The viability of the bap microparticles was investigated as a function of the amount of the bifidobacteria cultures, and the addition of a yeast extract, cryoprotectants, antioxidants and neutralizer. The size of the bap microparticles with and without the bifidobacteria was 84.8 +/- 28.5 microm (mean +/- standard deviation) and 113.1 +/- 38.5 microm, respectively. The surface morphology was slightly ellipsoid and wrinkled regardless of the incorporating bifidobacteria. The viability gradually decreased with increasing freeze-drying time. Free-flowing powdered bap microparticles were obtained at least 12 h after freeze-drying the wetted slurry of bap microparticles. However, the particles tended to aggregate when either lactose or ascorbic acid was added. The addition of a yeast extract, cryoprotectants (glycerol and lactose), antioxidants (NaHSO3 and ascorbic acid) and neutralizer (Mg3(PO4)2) resulted in a significantly higher viability of the bifidobacteria in the bap microparticles after freeze-drying (0.34-1.84 log) compared with the culture alone.

Alginates↗
PubMed2006

Corticotropin-releasing factor (CRF) and urocortin promote the survival of cultured cerebellar GABAergic neurons through the type 1 CRF receptor.

Corticotropin releasing factor (CRF) is known to be involved in the stress response and in some degenerative brain disorders. In addition, CRF has a role as a neuromodulator in adult cerebellar circuits. Data from developmental studies suggest a putative role for CRF as a trophic factor during cerebellar development. In this study, we investigated the trophic role for CRF family of peptides by culturing cerebellar neurons in the presence of CRF, urocortin or urocortin II. Primary cell cultures of cerebella from embryonic day 18 mice were established, and cells were treated for either 1, 5 or 9 days with Basal Medium Eagles complete medium alone or complete medium with 1 microM CRF, urocortin, or urocortin II. The number of GABA-positive neurons in each treatment condition was counted at each culture age for monitoring the changes in neuronal survival. Treatment with 1 microM CRF or 1 microM urocortin increased the survival of GABAergic neurons at 6 days in vitro and 10 days in vitro, and this survival promoting effect was abolished by treatment with astressin in the presence of those peptides. Based on these data, we suggest that CRF or urocortin has a trophic role promoting the survival of cerebellar GABAergic neurons in cultures.

Animals↗
PubMed2005

Linear free-energy analysis of mercury(II) and cadmium(II) binding to three-stranded coiled coils.

Investigators have studied how proteins enforce nonstandard geometries on metal centers to assess the question of how protein structures can define the coordination geometry and binding affinity of an active-site metal cofactor. We have shown that cysteine-substituted versions of the TRI peptide series [AcG-(LKALEEK)(4)G-NH(2)] bind Hg(II) and Cd(II) in geometries that are different from what is normally found with thiol ligands in aqueous solution. A fundamental question has been whether this structural perturbation is due to protein influence or a change in the metal geometry preference. To address this question, we have completed linear free-energy analyses that correlate the association of three-stranded coiled coils in the absence of a metal with the binding affinity of the peptides to the heavy metals, Hg(II) and Cd(II). In this paper, six new members of this family have been synthesized, replacing core leucine residues with smaller and less hydrophobic residues, consequently leading to varying degrees of self-association affinities. At the same time, studies with some smaller and longer sequenced peptides have also been examined. All of these peptides are seen to sequester Hg(II) and Cd(II) in an uncommon trigonal environment. For both metals, the binding is strong with micromolar dissociation constants. For binding of Hg(II) to the peptides, the dissociation constants range from 2.4 x 10(-)(5) M for Baby L12C to 2.5 x 10(-)(9) M for Grand L9C for binding of the third thiolate to a linear Hg(II)(pep)(2) species. The binding of Hg(II) to the peptide Grand L9C is similar in energetics for metal binding in the metalloregulatory protein, mercury responsive (merR), displaying approximately 50% trigonal Hg(II) formation at nanomolar metal concentrations. Approximately, 11 kcal/mol of the Hg(II)(Grand L9C)(3)(-) stability is due to peptide interactions, whereas only 1-4 kcal/mol stabilization results from Hg(II)(RS)(2) binding the third thiolate ligand. This further validates the hypothesis that the favorable tertiary interactions in protein systems such as merR go a long way in stabilizing nonnatural coordination environments in biological systems. Similarly, for the binding of Cd(II) to the TRI family, the dissociation constants range from 1.3 x 10(-)(6) M for Baby L9C to 8.3 x 10(-)(9) M for TRI L9C, showing a similar nature of stable aggregate formation.

Amino Acid Sequence↗
PubMed2005

CYP2D6 genotype, antidepressant use, and tamoxifen metabolism during adjuvant breast cancer treatment.

BACKGROUND: The efficacy of tamoxifen therapy for the treatment of breast cancer varies widely among individuals. Plasma concentrations of the active tamoxifen metabolite endoxifen are associated with the cytochrome P450 (CYP) 2D6 genotype. We examined the effects of concomitant use of selective serotonin reuptake inhibitor antidepressants, which are CYP2D6 enzyme inhibitors commonly prescribed to treat hot flashes in women who take tamoxifen, and genotypes for genes that encode tamoxifen-metabolizing enzymes on plasma concentrations of tamoxifen and its metabolites. METHODS: Eighty patients with newly diagnosed with breast cancer who were beginning tamoxifen therapy (20 mg/day orally), 24 of whom were taking CYP2D6 inhibitors, were genotyped for common alleles of the CYP2D6, CYP2C9, CYP3A5, and sulfotransferase (SULT) 1A1 genes. Plasma concentrations of tamoxifen and its metabolites were measured after 1 and 4 months of tamoxifen therapy. Differences in plasma concentrations of tamoxifen and its metabolites between genotype groups were analyzed by the Wilcoxon rank sum test. All statistical tests were two-sided. RESULTS: Among all women, plasma endoxifen concentrations after 4 months of tamoxifen therapy were statistically significantly lower in subjects with a CYP2D6 homozygous variant genotype (20.0 nM, 95% confidence interval [CI] = 11.1 to 28.9 nM) or a heterozygous genotype (43.1 nM, 95% CI = 33.3 to 52.9 nM) than in those with a homozygous wild-type genotype (78.0 nM, 95%CI = 65.9 to 90.1 nM) (both P = .003). Among subjects who carried a homozygous wild-type genotype, the mean plasma endoxifen concentration for those who were using CYP2D6 inhibitors was 58% lower than that for those who were not (38.6 nM versus 91.4 nM, difference = -52.8 nM, 95% CI = -86.1 to -19.5 nM, P = .0025). The plasma endoxifen concentration was slightly reduced in women taking venlafaxine, a weak inhibitor of CYP2D6, whereas the plasma endoxifen concentration was reduced substantially in subjects who took paroxetine (a potent inhibitor of CYP2D6). Genetic variations of CYP2C9, CYP3A5, or SULT1A1 had no statistically significant associations with plasma concentrations of tamoxifen or its metabolites. CONCLUSION: Interactions between CYP2D6 polymorphisms and coadministered antidepressants and other drugs that are CYP2D6 inhibitors may be associated with altered tamoxifen activity.

Adult↗
PubMed2004

Fluorous effect in proteins: de novo design and characterization of a four-alpha-helix bundle protein containing hexafluoroleucine.

Several studies have demonstrated that proteins incorporating fluorinated analogues of hydrophobic amino acids such as leucine and valine into their hydrophobic cores exhibit increased stability toward thermal denaturation and unfolding by guanidinium chloride. However, estimates for the increase in the thermodynamic stability of a protein (DeltaDeltaG(unfold)) afforded by the substitution of a hydrophobic amino acid with its fluorinated analogue vary quite significantly. To address this, we have designed a peptide that adopts an antiparallel four-helix bundle structure in which the hydrophobic core is packed with leucine, and investigated the effects of substituting the central two layers of the core with L-5,5,5,5',5',5'-hexafluoroleucine (hFLeu). We find that DeltaDeltaG(unfold) is increased by 0.3 kcal/mol per hFLeu residue. This is in good agreement with the predicted increase in DeltaDeltaG(unfold) of 0.4 kcal/mol per residue arising from the increased hydrophobicity of the hFLeu side chain, which we determined experimentally from partitioning measurements on hFLeu and leucine. The increased stability of this fluorinated protein may therefore be ascribed to simple hydrophobic effects, rather than specific "fluorous" interactions between the hFLeu residues.

Circular Dichroism↗
PubMed2004

Escherichia coli lipoyl synthase binds two distinct [4Fe-4S] clusters per polypeptide.

Lipoyl synthase (LS) is a member of a recently established class of metalloenzymes that use S-adenosyl-l-methionine (SAM) as the precursor to a high-energy 5'-deoxyadenosyl 5'-radical (5'-dA(*)). In the LS reaction, the 5'-dA(*) is hypothesized to abstract hydrogen atoms from C-6 and C-8 of protein-bound octanoic acid with subsequent sulfur insertion, generating the lipoyl cofactor. Consistent with this premise, 2 equiv of SAM is required to synthesize 1 equiv of the lipoyl cofactor, and deuterium transfer from octanoyl-d(15) H-protein of the glycine cleavage system-one of the substrates for LS-has been reported [Cicchillo, R. M., Iwig, D. F., Jones, A. D., Nesbitt, N. M., Baleanu-Gogonea, C., Souder, M. G., Tu, L., and Booker, S. J. (2004) Biochemistry 43, 6378-6386]. However, the exact identity of the sulfur donor remains unknown. We report herein that LS from Escherichia coli can accommodate two [4Fe-4S] clusters per polypeptide and that this form of the enzyme is relevant to turnover. One cluster is ligated by the cysteine amino acids in the C-X(3)-C-X(2)-C motif that is common to all radical SAM enzymes, while the other is ligated by the cysteine amino acids residing in a C-X(4)-C-X(5)-C motif, which is conserved only in lipoyl synthases. When expressed in the presence of a plasmid that harbors an Azotobacter vinelandii isc operon, which is involved in Fe/S cluster biosynthesis, the as-isolated wild-type enzyme contained 6.9 +/- 0.5 irons and 6.4 +/- 0.9 sulfides per polypeptide and catalyzed formation of 0.60 equiv of 5'-deoxyadenosine (5'-dA) and 0.27 equiv of lipoylated H-protein per polypeptide. The C68A-C73A-C79A triple variant, expressed and isolated under identical conditions, contained 3.0 +/- 0.1 irons and 3.6 +/- 0.4 sulfides per polypeptide, while the C94A-C98A-C101A triple variant contained 4.2 +/- 0.1 irons and 4.7 +/- 0.8 sulfides per polypeptide. Neither of these variant proteins catalyzed formation of 5'-dA or the lipoyl group. Mössbauer spectroscopy of the as-isolated wild-type protein and the two triple variants indicates that greater than 90% of all associated iron is in the configuration [4Fe-4S](2+). When wild-type LS was reconstituted with (57)Fe and sodium sulfide, it harbored considerably more iron (13.8 +/- 0.6) and sulfide (13.1 +/- 0.2) per polypeptide and catalyzed formation of 0.96 equiv of 5'-dA and 0.36 equiv of the lipoyl group. Mössbauer spectroscopy of this protein revealed that only approximately 67% +/- 6% of the iron is in the form of [4Fe-4S](2+) clusters, amounting to 9.2 +/- 0.4 irons and 8.8 +/- 0.1 sulfides or 2 [4Fe-4S](2+) clusters per polypeptide, with the remainder of the iron occurring as adventitiously bound species. Although the Mössbauer parameters of the clusters associated with each of the variants are similar, EPR spectra of the reduced forms of the cluster show small differences in spin concentration and g-values, consistent with each of these clusters as distinct species residing in each of the two cysteine-containing motifs.

Amino Acid Motifs↗
PubMed2004

Control of metal coordination number in de novo designed peptides through subtle sequence modifications.

Substitution of an alanine for leucine (shown in light blue) in the hydrophobic interior of designed three-stranded coiled coils allows for the control of metal ion coordination number and geometry. The influence of this perturbation by a noncoordinating residue can be monitored by the dramatic impact on the 113Cd NMR spectrum. The structural effect occurs even when the residue substitution is as much as 7 A from the metal binding site.

Amino Acid Sequence↗
PubMed2004

Corticotropin releasing factor enhances survival of cultured GABAergic cerebellar neurons after exposure to a neurotoxin.

Corticotropin-releasing factor (CRF), in addition to its role as a hormone in the stress response, functions as a neuromodulator in the cerebellum, where it enhances both the spontaneous and amino acid induced firing rate of Purkinje cells. In the cerebellum, CRF and its two types of receptors (CRF-R(1) and CRF-R(2)) are present during cerebellar development at ages that precede the onset of afferent ingrowth and synaptogenesis, suggesting a distinct role during early cerebellar development. The present study was undertaken to determine whether CRF enhances the survival of cerebellar neurons, in particular GABAergic neurons. Primary cultures of cerebellar neurons obtained from embryonic day 18 mice were composed primarily, but not exclusively, of GABAergic neurons. Although CRF-R(1) is present in most neurons in this culture system, when CRF was added to the medium, no significant change in neuronal survival was observed when compared to control cultures. It is possible that a role for CRF is not seen in growth-promoting culture medium at the plating density chosen for this study and may only be evident when the cells have been exposed to conditions that reduce the likelihood of survival, such as exposure to neurotoxins such as AraC. We propose that, because AraC increases the number of cleaved caspase-3 positive cells, indicating apoptosis, it is possible that a CRF effect involves an inhibition of the apoptotic pathway. Cultures treated with AraC had a decrease in the total number of GABAergic neurons and an increase in apoptotic cells as measured with the apoptotic marker cleaved caspase-3. Co-treatment with CRF rescued many GABAergic neurons. It is interesting to note that apoptotic cells do not exhibit GABA or c-fos positive immunolabeling. Thus, these data support the concept that CRF plays a neuroprotective role in the survival of GABAergic cerebellar neurons in culture after exposure to a neurotoxin.

Animals↗
PubMed2004

Pharmacological characterization of 4-hydroxy-N-desmethyl tamoxifen, a novel active metabolite of tamoxifen.

The antiestrogen tamoxifen is extensively metabolized in patients to form a series of compounds with altered affinity for estrogen receptors (ERs), the primary target of this drug. Furthermore, these metabolites exhibit a range of partial agonist and antagonist activities for ER mediated effects that do not depend directly on their absolute affinity for ERs. Thus, clinical response to tamoxifen therapy is likely to depend on the aggregate effect of these different metabolites resulting from their abundance in the patient, their affinity for the receptors, and their agonist/antagonist profile. A recent study has shown that plasma concentrations of the tamoxifen metabolite 4-hydroxy- N -desmethyl tamoxifen (endoxifen), in patents undergoing tamoxifen therapy, are dependent on the cytochrome p450 (CYP) 206 ge notype of the patient and that medications commonly prescribed to patients on tamoxifen therapy can also inhibit endoxifen production. In this study we characterized the properties of this metabolite with respect to binding to ERs, ability to inhibit estrogen stimulated breast cancer cell proliferation and the regulation of estrogen responsive genes. We demonstrate that endoxifen has essentially equivalent activity to the potent metabolite 4-hydroxy tamoxifen (4-OH-tam) often described as the active metabolite of this drug. Since plasma levels of endoxifen in patients with functional CYP2D6 frequently exceed the levels of 4-OH-tam, it seems likely that endoxifen is at least as important as 4-OH-tam to the overall activity of this drug and suggests that CYP2D6 status and concomitant administration of drugs that inhibit CYP2D6 activity have the potential to affect response to tamoxifen therapy.

Breast Neoplasms↗
PubMed2004

A population pharmacokinetic model with time-dependent covariates measured with errors.

We propose a population pharmacokinetic (PK) model with time-dependent covariates measured with errors. This model is used to model S-oxybutynin's kinetics following an oral administration of Ditropan, and allows the distribution rate to depend on time-dependent covariates blood pressure and heart rate, which are measured with errors. We propose two two-step estimation methods: the second-order two-step method with numerical solutions of differential equations (2orderND), and the second-order two-step method with closed form approximate solutions of differential equations (2orderAD). The proposed methods are computationally easy and require fitting a linear mixed model at the first step and a nonlinear mixed model at the second step. We apply the proposed methods to the analysis of the Ditropan data, and evaluate their performance using a simulation study. Our results show that the 2orderND method performs well, while the 2orderAD method can yield PK parameter estimators that are subject to considerable biases.

Biometry↗
PubMed2003

Quantification of tamoxifen and three metabolites in plasma by high-performance liquid chromatography with fluorescence detection: application to a clinical trial.

A sensitive and reproducible assay employing liquid-liquid extraction and high-performance liquid chromatography with fluorescence detection for the quantification of tamoxifen, N-desmethyltamoxifen, 4-hydroxytamoxifen, and Z-4-hydroxy-N-desmethyltamoxifen in human plasma is described. The compounds and internal standard, propranolol, were separated with a cyano column and a mobile phase of acetonitrile-20 mM potassium phosphate buffer (pH 3; 35:65, v/v) then detected with fluorescence using a modified version of a method originally described by Fried and Wainer [J. Chromatogr. B 655 (1994) 261]. The coefficients of variation for the midpoint of the standard curve for each compound were less than 10%. This method was applied to a pharmacokinetic study of tamoxifen disposition in breast cancer patients.

Antineoplastic Agents, Hormonal↗