Eric Ezan

Cea Leti, Grenoble, Rhône-Alpes, France

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Publications (50)218.2 Total impact

  • F Becher · E Duriez · H Volland · J C Tabet · E Ezan
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    ABSTRACT: The toxin ricin is a biological weapon that may be used for bioterrorist purposes. As a member of the group of ribosome-inactivating proteins (RIPs), ricin has an A-chain possessing N-glycosidase activity which irreversibly inhibits protein synthesis. In this paper, we demonstrate that provided appropriate sample preparation is used, this enzymatic activity can be exploited for functional ricin detection with sensitivity similar to the best ELISA and specificity allowing application to environmental samples. Ricin is first captured by a monoclonal antibody directed against the B chain and immobilized on magnetic beads. Detection is then realized by determination of the adenine released by the A chain from an RNA template using liquid chromatography coupled to tandem mass spectrometry. The immunoaffinity step combined with the enzymatic activity detection leads to a specific assay for the entire functional ricin with a lower limit of detection of 0.1 ng/mL (1.56 pM) after concentration of the toxin from a 500 microL sample size. The variability of the assay was 10%. Finally, the method was applied successfully to milk and tap or bottled water samples.
    Analytical Chemistry 02/2007; 79(2):659-65. DOI:10.1021/ac061498b · 5.64 Impact Factor
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    ABSTRACT: In higher plants and some fungi, heavy metals induce the synthesis of chelating peptides known as phytochelatins (PCs). They are characterized by the general structure (gamma-Glu-Cys)n-Gly, but in some plant species, the C-terminal glycine can be replaced by serine, glutamine, glutamate or alanine, leading to iso-phytochelatins (iso-PCs). Although the distribution of iso-PCs is considered to differ from one species to another, we previously showed that Arabidopsis thaliana (A. thaliana) cells are able to synthesize most PC-related peptides (PCs and iso-PCs) described in the literature. We also observed an accumulation of the dipeptide gamma-glutamylcysteine (gamma-EC) when cadmium (Cd) (200 microM) was added to the culture medium, suggesting that either glutathione synthetase or glycine availability could be a limiting factor for the biosynthesis of PC-related peptides. In this context, the aim of the present work was to seek new insights into the regulation of PC synthesis by performing metabolic profiling using liquid chromatography-mass spectrometry. The levels of PC-related peptides and their precursors were measured in A. thaliana cells following Cd exposure. A range of doses (0, 50, 200 and 400 microM CdNO3) and kinetic studies (from 1 to 48 h) showed a dose threshold (50 microM CdNO3) and a lag time between the appearance of PCs and iso-PCs concomitant with the gamma-EC accumulation induced by Cd, occurring at cadmium concentrations above 50 microM. This accumulation was suppressed by supplementation of the culture medium with 25 mM glycine. Glycine supplementation had a limited impact on the concentrations of glutathione and PCs whereas the levels of most iso-PCs were significantly increased. Taken together, these results indicate that GSH is involved in the biosynthesis of the iso-PCs in vivo, and that the biosynthesis of PC-related peptides is limited by the availability of glycine in the presence of high cadmium concentrations.
    Biochimie 12/2006; 88(11):1733-42. DOI:10.1016/j.biochi.2006.08.005 · 2.96 Impact Factor
  • F Becher · A Pruvost · G Clement · J C Tabet · E Ezan
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    ABSTRACT: LC/ESI-MS/MS is a promising alternative to immunoassays in improving the analysis of recombinant therapeutic proteins in biological fluids for toxicity and pharmacokinetics purposes. To assess the sensitivity and validation issues associated with this technique, we use here as a model EPI-hNE4, a 56-amino acid recombinant protein, and demonstrate that a method based on tandem mass spectrometry combined with liquid chromatography and electrospray interface can reach sensitivity similar to that of ELISA but without its potential cross-reactivity. For this purpose, a triple quadrupole mass spectrometer operating in positive ion and single reaction monitoring mode with transition, m/z 1040 --> 1224.5, was used for selective peak detection. Particular issues related to the internal standard, i.e., elution and ionization patterns similar to the protein without stable isotope labeling, and to analytical interference due to endogenous binding antibodies were addressed. A limit of quantification in human or monkey plasma of 5 ng/mL was reached with a sample volume of 100 microL, corresponding to 40 fmol injected into the HPLC column. Intra- and interassay precision and accuracy were below 15%. No matrix effect was detected.
    Analytical Chemistry 05/2006; 78(7):2306-13. DOI:10.1021/ac0515531 · 5.64 Impact Factor
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    ABSTRACT: The blood-brain barrier (BBB) permeabilities of 11 compounds were measured both in vitro with a newly developed coculture-based model of human BBB and in vivo with positron emission tomography (PET). The 11 compounds were fluoropyridinyl derivatives labeled with the positron-emitter fluorine-18, [(18)F]F-A-85380 [2-[(18)F]fluoro-3-[2(S)-2 azetidinylmethoxy]pyridine], and 10 selected N-substituted-azetidinyl and pyrrolidinyl closely related [(18)F]fluoropyridinyl derivatives (including [N'-aromatic/aliphatic]-thioureas, -ureas, and -amides). The in vitro BBB model, a new coculture system of primary human brain endothelial cells and astrocytes, was used to measure the permeability coefficient for each compound. Dynamic PET studies were performed in rats with the same compounds, and a two-compartment model analysis was used to calculate their in vivo permeability coefficients. The 11 derivatives differed in their degree of BBB passage and transport mechanism. The analysis of PET data showed a significant cerebral uptake for six derivatives, for which the in vitro evaluation indicated active influx or free diffusion. Five derivatives displayed low in vivo cerebral uptake, in agreement with the observation of an in vitro active efflux. Overall, there was a remarkable correlation between the in vitro and in vivo permeability coefficients (r = 0.99). This double study proves a close correlationship between the assessment of the BBB passage in vitro and in vivo. The in vitro model of human BBB offers the possibility of subtle discrimination of various BBB permeability degrees and transport mechanisms. Conversely, small animal PET imaging appears suitable to screen directly in vivo brain targeting of drugs or radiopharmaceutical candidates.
    Journal of Pharmacology and Experimental Therapeutics 02/2006; 316(1):79-86. DOI:10.1124/jpet.105.089102 · 3.97 Impact Factor
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    ABSTRACT: This report describes a concept in which an immunoassay is used indirectly to quantify a nonantigenic very low molecular weight compound participating in a chemical reaction with a haptenic reporter. The detection limit of each reagent is, therefore, governed only by the affinity of the antibodies toward the reporter. Fluoride was used as a model, and silylated estradiol was used as a reporter. Upon silylation with N-O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) or N-O-bis(dimethylterbutylsilyl) trifluoroacetamide (MTBSTFA), estradiol is no longer recognized by antibodies specific to estradiol. After reaction with hydrofluoric acid (HF) or fluoride salts (KF, CsF, NaF), its immunoreactivity is restored, and native estradiol is formed and is detected by immunoassay. The level of synthesized estradiol is dependent on the concentration of fluoride. A fluoride detection limit of 0.3 microg/L (15 nM) is obtained. Potential interference with other acids has been eliminated by choosing the silyl group (trimethylsilyl vs tert-butyldimethylsilyl) and by selecting optimal reaction conditions for the desilylation. The method has been applied to the detection of fluoride salts in natural waters (range 0.28-9.0 mg/L) and in an atmosphere artificially contaminated with HF between 8 and 160 microg/m(3) in the parts-per-billion range. This indirect immunoassay combines simplicity and high sensitivity and, therefore, can be used in field monitoring. Finally, the extension of the concept to other chemicals is discussed.
    Analytical Chemistry 09/2004; 76(15):4286-91. DOI:10.1021/ac030395f · 5.64 Impact Factor
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    ABSTRACT: Angiotensin I-converting enzyme (ACE) inhibitors can affect hematopoiesis by several mechanisms including inhibition of angiotensin II formation and increasing plasma concentrations of AcSDKP (acetyl-N-Ser-Asp-Lys-Pro), an ACE substrate and a negative regulator of hematopoiesis. We tested whether ACE inhibition could decrease the hematopoietic toxicity of lethal or sublethal irradiation protocols. In all cases, short treatment with the ACE inhibitor perindopril protected against irradiation-induced death. ACE inhibition accelerated hematopoietic recovery and led to a significant increase in platelet and red cell counts. Pretreatment with perindopril increased bone marrow cellularity and the number of hematopoietic progenitors (granulocyte macrophage colony-forming unit [CFU-GM], erythroid burst-forming unit [BFU-E], and megakaryocyte colony-forming unit [CFU-MK]) from day 7 to 28 after irradiation. Perindopril also increased the number of hematopoietic stem cells with at least a short-term reconstitutive activity in animals that recovered from irradiation. To determine the mechanism of action involved, we evaluated the effects of increasing AcSDKP plasma concentrations and of an angiotensin II type 1 (AT1) receptor antagonist (telmisartan) on radioprotection. We found that the AT1-receptor antagonism mediated similar radioprotection as the ACE inhibitor. These results suggest that ACE inhibitors and AT1-receptor antagonists could be used to decrease the hematopoietic toxicity of irradiation.
    Blood 09/2004; 104(4):978-85. DOI:10.1182/blood-2003-11-3828 · 10.45 Impact Factor
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    ABSTRACT: P-glycoprotein (P-gp) is a multidrug transporter responsible for resistance to anticancer chemotherapy and physiologically involved in absorption, distribution, and excretion of a large number of hydrophobic xenobiotics. P-gp exhibits both an ATPase activity correlated with its drug transport function and a basal ATPase activity in the absence of any drug. We have developed a high-throughput screening test to detect specific interactions between drugs and P-gp. We took into account the existence of multiple binding sites on P-gp to propose and validate an optimized strategy, based on the modulation of the basal ATPase activity of P-gp and of the ATPase activity stimulated by three reference substrates (verapamil, vinblastine, and progesterone). The ATPase activity measurements were performed on P-gp-containing membrane vesicles from actinomycin-D-selected hamster DC-3F lung fibroblasts by a spectrophotometric method based on continuous monitoring of ADP formation, regenerated in ATP by a coupled enzyme system. This assay may be performed on 96- or 384-well microtiter plates. When applying this ATPase assay to 41 compounds known from the literature for their interaction with P-gp, 95% of them were found to be positive, whereas only 78% were positive when considering solely the modulation of the basal activity.
    Analytical Biochemistry 07/2002; 305(1):106-14. DOI:10.1006/abio.2002.5650 · 2.22 Impact Factor
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    ABSTRACT: The growing array of in vitro models of the blood-brain barrier (BBB) which have been used makes it difficult to draw firm conclusions concerning the BBB penetration of HIV-1 protease inhibitors. What is needed is a combined in vivo and in vitro study on biological models that mimic as closely as possible the normal human BBB, to establish whether and how indinavir crosses the BBB. We developed a new human BBB model using primary endothelial cells and astrocytes. The biological relevance of this model was checked with respect on the one hand, to the close relationship between the log of drug permeability coefficient normalized to molecular weight and the log of the 1-octanol/water partition coefficient, and on the other hand to the functional P-glycoprotein (P-gp) expression. We employed this model to perform transport studies with indinavir and showed that the rate of in vitro indinavir transport from the basal to apical compartment was higher than the rate of apical to basal transport. Pretreatment of the BBB model with the P-gp inhibitor, quinidine, significantly increased apical to basal transport. Intracellular indinavir accumulation was increased in BBB as a result of inhibition of active transport. These data were correlated with the indinavir-mediated P-gp ATPase modulation showing that indinavir specifically interacted with a binding site on P-gp. Moreover, the activation of P-gp ATPase by indinavir was inhibited by quinidine. In addition, the in vivo brain to plasma concentration ratio of indinavir into mice showed that indinavir concentration was up to five times higher in the brain of mdr1a(-/-) mice than in the brain of mdr1a(+/+) mice. All these results confirm the role of P-gp in preventing the passage of indinavir across BBB and thus its entry into the central nervous system (CNS). Our human BBB model represents a useful tool for the evaluation of drug penetration into the CNS.
    Brain Research 03/2002; 927(2):153-67. DOI:10.1016/S0006-8993(01)03337-6 · 2.84 Impact Factor
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    ABSTRACT: 1. Angiotensin I-converting enzyme (ACE) has two homologous active N- and C-terminal domains and displays activity towards a broad range of substrates. The tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) has been shown to be hydrolysed in vitro by ACE and to be a preferential substrate for its N-terminal active site. This peptide reversibly prevents the recruitment of pluripotent haematopoietic stem cells and normal early progenitors into the S-phase. 2. Angiotensin I-converting enzyme inhibitors, given as a single dose to normal subjects or during long-term treatment in hypertensive patients, result in plasma AcSDKP levels five- to six-fold higher and urine concentrations 40-fold higher than those of control subjects and/or patients. Thus, AcSDKP is a natural peptide hydrolysed by the N-terminal domain of ACE in vivo. In addition, ACE may be implicated in the process of haematopoietic stem cell regulation by permanently degrading this natural circulating inhibitor of cell entry into the S-phase. 3. Besides hydrolysis by ACE, the second very effective mechanism by which AcSDKP is cleared from plasma is glomerular filtration. Because of its high sensitivity and specificity, the measurement of AcSDKP in plasma and urine provides a valuable tool in screening specific inhibitors of the N-terminal domain of ACE and in monitoring ACE inhibition during chronic treatment. 4. The long-term consequences of AcSDKP accumulation are not known. During chronic ACE inhibition in rats, AcSDKP levels slightly increase in organs with high ACE content (kidneys, lungs). To significantly increase its concentration in target haematopoietic organs (the extracellular fraction of bone marrow), AcSDKP has to be infused on top of a captopril-based treatment. 5. A selective inhibitor of the N-domain of ACE in vitro and in vivo has been identified recently. The phosphinic peptide RXP 407 does not interfere with blood pressure regulation, but does increase, dose dependently, plasma concentrations of AcSDKP in mice, in contrast with lisinopril, which affects the metabolism of both AcSDKP and angiotensin I. N-Terminal-selective ACE inhibitors may be used to selectively control AcSDKP metabolism in target haematopoietic organs. This new therapeutic strategy may be of value for protecting haematopoietic cells from the toxicity of cancer chemotherapy.
    Clinical and Experimental Pharmacology and Physiology 01/2002; 28(12):1066-9. DOI:10.1046/j.1440-1681.2001.03560.x · 2.37 Impact Factor
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    ABSTRACT: The phosphinic peptide RXP 407 has recently been identified as the first potent selective inhibitor of the N-active site (domain) of angiotensin-converting enzyme (ACE) in vitro. The aim of this study was to probe the in vivo efficacy of this new ACE inhibitor and to assess its effect on the metabolism of AcSDKP and angiotensin I. In mice infused with increasing doses of RXP 407 (0.1--30 mg/kg/30 min), plasma concentrations of AcSDKP, a physiological substrate of the N-domain, increased significantly and dose dependently toward a plateau 4 to 6 times the basal levels. RXP 407 significantly and dose dependently inhibited ex vivo plasma ACE N-domain activity, whereas it had no inhibitory activity toward the ACE C-domain. RXP 407 (10 mg/kg) did not inhibit the pressor response to an i.v. angiotensin I bolus injection in mice. In contrast, lisinopril infusion (5 and 10 mg/kg/30 min) affected the metabolism of both AcSDKP and angiotensin I. Thus, RXP 407 is the first ACE inhibitor that might be used to control selectively AcSDKP metabolism with no effect on blood pressure regulation.
    Journal of Pharmacology and Experimental Therapeutics 06/2001; 297(2):606-11. · 3.97 Impact Factor
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    ABSTRACT: N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural inhibitor of pluripotent hematopoietic stem cell proliferation. Ac-SDKP plasma concentration is increased 5-fold after angiotensin-converting enzyme inhibition. Here we studied the effect of Ac-SDKP on monocyte/macrophage infiltration, fibroblast proliferation, and collagen deposition in the rat heart in renovascular hypertension. We investigated whether long-term Ac-SDKP administration would prevent left ventricular (LV) hypertrophy and interstitial collagen deposition in rats with 2-kidney, 1-clip (2K-1C) hypertension. Ac-SDKP (400 microgram. kg(-1). d(-1)) did not affect development of hypertension. Mean blood pressure was similar in rats with 2K-1C hypertension whether they were given vehicle or Ac-SDKP and was higher than in controls. Both LV weight and cardiomyocyte size were significantly increased in rats with 2K-1C hypertension compared with controls and were unaffected by Ac-SDKP. Proliferating cell nuclear antigen- and monocyte/macrophage-positive cells were increased in the LV of 2K-1C hypertensive rats; this increase was significantly blunted by Ac-SDKP (P<0.001). LV interstitial collagen fraction was also increased in 2K-1C hypertensive rats given vehicle (10.1+/-0.8%) compared with sham (5.3+/-0.1%, P<0.0001), and this increase was prevented by Ac-SDKP (5.4+/-0.4%, P<0.001). Ac-SDKP inhibited monocyte/macrophage infiltration, cell proliferation, and collagen deposition in the LV of hypertensive rats without affecting blood pressure or cardiac hypertrophy, suggesting that it may be partly responsible for the cardioprotective effect of angiotensin-converting enzyme inhibitors.
    Circulation 06/2001; 103(25):3136-41. DOI:10.1161/01.CIR.103.25.3136 · 14.43 Impact Factor
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    ABSTRACT: In order to determine nicergoline pharmacokinetics after oral administration to humans, we have developed two radioimmunoassays, one directed against nicergoline and the other directed against known nicergoline metabolites. The assays were validated according to the recommendations of international regulatory agencies and their limits of quantification were 40 and 10 pg/ml, respectively. In order to further validate the methods, a chromatographic separation of immunoreactive entities was performed with samples from healthy volunteers who were given 15 mg of Sermion (nicergoline orally administered). Chromatographic determination of assay specificity showed that the metabolite radioimmunoassay recognised known nicergoline metabolites but also a new metabolite. Using the antibodies directed against nicergoline, we were unable to detect nicergoline in the human plasma. This suggests that nicergoline is absent in the circulation because of complete metabolism through its first-pass effect.
    Journal of Pharmaceutical and Biomedical Analysis 05/2001; 25(1):123-30. DOI:10.1016/S0731-7085(00)00501-X · 2.98 Impact Factor
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    ABSTRACT: The tetrapeptide AcSDKP, a natural and specific substrate of angiotensin I-converting enzyme (ACE), is a negative regulator of hematopoiesis. AcSDKP has been measured in various biological media using an enzyme immunoassay (EIA), but its presence in human plasma and urine has not been formally established. By using immunoaffinity extraction and liquid chromatography-electrospray mass spectrometry, we demonstrate that AcSDKP-like immunoreactivity measured with EIA in plasma and urine samples from untreated, captopril- (an ACE inhibitor) and AcSDKP-treated subjects corresponds to AcSDKP. The present study confirms that AcSDKP is naturally present in human plasma and urine and that EIA is reliable for its measurement in such media.
    Journal of chromatography. B, Biomedical sciences and applications 04/2001; 752(1):69-75. DOI:10.1016/S0378-4347(00)00520-X
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    ABSTRACT: The tetrapeptide Acetyl-Ser-Asp-Lys-Pro (AcSDKP) has been shown to protect hematopoietic stem cells from the toxicity of anticancer chemotherapies. Since its pharmacological efficacy is limited by a rapid degradation by Angiotensin-I Converting Enzyme (ACE), AcSDKP analogs resistant to ACE have been synthesized. One of these compounds (AcSDKP-NH,) differs from the native AcSDKP by amidation of the C-terminus. Further evaluations of this molecule require an analytical method in order to characterize its pharmacokinetic profile. We report, here, the development of a highly specific and sensitive enzyme immunoassay (EIA) for AcSDKP-NH, thatdoes not cross-react with endogenous or exogenous AcSDKP. Using AcSDKP-NH2-acetylcholinesterase conjugate as a tracer, rabbit specific antiserum and microtiter plates coated with goat anti-rabbit immunoglobulins, this EIA allows the determination of AcSDKP-NH2 with limits of quantitation of 1 nM in mouse plasma and 100 pmol/g in tissues. Intra-day and inter-day coefficients of variations were less than 20%. The method was successfully applied to a pharmacokinetic study in order to compare plasma and tissue profiles of AcSDKP-NH2 and AcSDKP. Plasma AcSDKP-NH2 levels were found higher than those of AcSDKP, with AUCinf and Cmax values, respectively, 26- and 10-fold higher than that of AcSDKP.
    Journal of Immunoassay and Immunochemistry 02/2001; 22(1):15-31. DOI:10.1081/IAS-100102895 · 0.73 Impact Factor
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    ABSTRACT: While nephrologists often observe reduced hematocrit associated with inhibitors of angiotensin-converting enzyme (ACE), the basis for this effect is not well understood. We now report that two strains of ACE knockout mice have a normocytic anemia associated with elevated plasma erythropoietin levels. (51)Cr labeling of red cells showed that the knockout mice have a normal total blood volume but a reduced red cell mass. ACE knockout mice, which lack tissue ACE, are anemic despite having normal renal function. These mice have increased plasma levels of the peptide acetyl-SDKP, a possible stem cell suppressor. However, they also show low plasma levels of angiotensin II. Infusion of angiotensin II for 2 weeks increased hematocrit to near normal levels. These data suggest that angiotensin II facilitates erythropoiesis, a conclusion with implications for the management of chronically ill patients on inhibitors of the renin-angiotensin system.
    Journal of Clinical Investigation 01/2001; 106(11):1391-8. DOI:10.1172/JCI10557 · 13.22 Impact Factor
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    ABSTRACT: Angiotensin I-converting enzyme (ACE) has been shown to be involved in the catabolism of the tetrapeptide acetyl-Ser-Asp-Lys-Pro (AcSDKP). As AcSDKP is a physiological inhibitor of haematopoietic stem cell proliferation, we investigated the in vitro and in vivo effects of captopril, one of the specific inhibitors of ACE, on the proliferation of primitive haematopoietic cells. Regenerating bone marrow cells obtained from mice given one injection of cytosine arabinoside (100 mg/kg) as well as SA2 myeloid leukaemia cells were incubated in vitro for 24 h with 10-6 M captopril. Captopril significantly reduced the proportion of high proliferative potential colony-forming cells (HPP-CFC-1) in S-phase, whereas it had no effect on the proportion of SA2 leukaemic colony-forming cells in S-phase. When given in vivo to mice 1 h after 2 Gy gamma-irradiation or cytosine arabinoside (AraC) injection, captopril (100 mg/kg) was shown to prevent HPP-CFC-1 entry into S-phase induced by these cytotoxic treatments. The observed effects correlated with a reduction in ACE degradative activity and an increase in the level of endogenous AcSDKP both in the supernatants of captopril-treated bone marrow cells and in plasma of treated animals. The present findings suggest that AcSDKP might mediate the observed in vitro and in vivo inhibitory effects of captopril on primitive haematopoietic cell proliferation.
    British Journal of Haematology 07/2000; 109(3):563-70. DOI:10.1046/j.1365-2141.2000.02073.x · 4.71 Impact Factor
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    ABSTRACT: Bromocriptine, a D2 receptor agonist, was administered intravenously (1mg/kg) to anesthetized rats. Microdialysis probes were implanted in the pituitary and the striatum, known sites of D2 agonist action. Bromocriptine and its metabolites were monitored in plasma and tissue dialysates for 4 h. Drug analyses were performed using two different enzyme immunoassays specific for untransformed bromocriptine or a pool of parent drug plus hydroxylated metabolites. The metabolites/parent drug ratio for areas under the curve was 5.5 in plasma and 1 in the pituitary. No metabolites could be detected in the striatum. Bromocriptine penetration was at least 10-fold greater in the pituitary than in the striatum. The kinetics of bromocriptine in the pituitary and striatum did not parallel those in plasma, indicating that the prolonged action of bromocriptine reported by other authors may be due to slow dissociation from receptors.
    European Journal of Drug Metabolism and Pharmacokinetics 06/2000; 25(2):79-84. DOI:10.1007/BF03190071 · 1.56 Impact Factor
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    ABSTRACT: Since currently used assays of amphotericin B (AMB) lack sensitivity or are not easily adaptable in all laboratories, we have developed an enzyme immunoassay for AMB in biological fluids and tissues. Antibodies to AMB were raised in rabbits after administration of an AMB-bovine serum albumin conjugate. The enzymatic tracer was obtained by coupling AMB via its amino group to acetylcholinesterase (EC These reagents were used for the development of a competitive immunoassay performed on microtitration plates. The limit of quantification was 100 pg/ml in plasma and 1 ng/g in tissues. The plasma assay was performed directly without extraction on a minimal volume of 0.1 ml. The intra- and interassay coefficients of variation were in the range of 5 to 17%, and the recoveries were 92 to 111% for AMB added to human plasma. The assay was applied to a pharmacokinetic study with mice given AMB intraperitoneally at the dose of 1 mg/kg. The drug distribution in selected compartments (plasma, liver, spleen, lung, and brain) was monitored until 72 h after administration. In conclusion, our assay is at least 100-fold more sensitive than previously described bioassays or chromatographic determinations of AMB and may be useful in studying the tissue pharmacokinetics of new AMB formulations and in drug monitoring in clinical situations.
    Antimicrobial Agents and Chemotherapy 04/2000; 44(3):546-50. DOI:10.1128/AAC.44.3.546-550.2000 · 4.48 Impact Factor
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    ABSTRACT: The tetrapeptide N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (AcSDKP) is a natural regulator of hematopoietic stem cell proliferation. The present study was aimed at investigating the presence and the role of AcSDKP in rat testis. Specific immunoreactivity was always observed in the interstitial tissue at all stages of testicular development and in elongated spermatids at 45 days of age and in adults. In accordance with the interstitial labeling, high AcSDKP levels were detected in Leydig cell and testicular macrophage culture media and cell extracts, as well as in the testicular interstitial fluid (TIF). Much lower concentrations were found in peritubular cells and Sertoli cells cultures, whereas very low concentrations were present in cultured spermatocytes and spermatids. In contrast to the slight degradation rate of AcSDKP observed in the spermatocyte and spermatid culture media, no catabolism of the peptide was seen in testicular somatic cell culture medium. Furthermore, the degradation rate of AcSDKP was much lower in TIF than in peripheral blood plasma. Despite the very strong evidence indicating that Leydig cells and testicular macrophages produce AcSDKP, the selective destruction of these cells did not result in any change in AcSDKP levels in TIF or in plasma. This suggests a compensatory mechanism ensuring constant levels of the peptide in TIF when interstitial cells are absent. Finally, in vitro, in the presence of AcSDKP, significantly more [(3)H]thymidine incorporation was found in A spermatogonia. In conclusion, this study establishes the presence of very high concentrations of AcSDKP in rat testis and demonstrates its Leydig cell and testicular macrophage origin. The presence of AcSDKP in the TIF and its stimulatory effect on thymidine incorporation in spermatogonia very strongly suggest its implication in the paracrine control of spermatogenesis.
    Journal of Cell Science 02/2000; 113 ( Pt 1):113-21. · 5.43 Impact Factor

Publication Stats

1k Citations
218.20 Total Impact Points


  • 1995–2007
    • Cea Leti
      Grenoble, Rhône-Alpes, France
  • 1996–2002
    • Institute of Geophysics, China Earthquake Administration
      Peping, Beijing, China
  • 2001
    • Natural Product Chemistry Institute
      Lutetia Parisorum, Île-de-France, France
  • 2000
    • Ninewells Hospital
      • Department of Surgery
      Dundee, Scotland, United Kingdom
  • 1994–2000
    • Atomic Energy and Alternative Energies Commission
      • Pharmacology and Immunoanalysis (SPI)
      Fontenay, Île-de-France, France