RESUMEN

Amprenavir is a human immunodeficiency virus-1 (HIV-1) protease inhibitor intended to be used to treat HIV-infected children. Although a pediatric dosage is proposed by the manufacturer, no data are currently available on the pharmacokinetics of amprenavir in neonates and infants. Amprenavir being primarily eliminated after oxidative biotransformation, we explored its in vitro metabolism by cytochrome P450 (P450)-dependent monooxygenases. In our conditions, five metabolites were formed in vitro and subsequently analyzed by liquid chromatography-mass spectrometry; P450-dependent oxidations occurred either on the tetrahydrofuran ring (M3 and M4), the aniline ring (M5), and the aliphatic chain (M2) or resulted from the N-dealkylation and loss of the tetrahydrofuran ring (M1). The two major metabolites, respectively M3 and M2 were formed by human liver microsomes with K(m) between 10 and 70 microM. CYP3A4 and to a lesser extent CYP3A5 were major contributors for the formation of M2, M3, and M5 metabolites, whereas CYP3A7 had no or little activity. This assumption was confirmed by inhibition with ketoconazole and ritonavir (two potent inhibitors of CYP3A) whereas sulfaphenazole (2C9 inhibitor) and quinidine (2D6 inhibitor) were inefficient. The metabolism of amprenavir was negligible in microsomes from either fetuses or neonates and steadily increased after the first weeks of life in relation with the maturation of CYP3A4/5. In conclusion, results demonstrated that the capacity of the human liver to oxidize amprenavir is low during the first weeks after birth and that dosage could be substantially reduced during the early neonatal period.

Asunto(s)

Sistema Enzimático del Citocromo P-450/fisiología , Feto/metabolismo , Hígado/embriología , Hígado/enzimología , Sulfonamidas/metabolismo , Adulto , Carbamatos , Células Cultivadas , Citocromo P-450 CYP3A , Sistema Enzimático del Citocromo P-450/biosíntesis , Sistema Enzimático del Citocromo P-450/metabolismo , Feto/enzimología , Furanos , Humanos , Lactante , Recién Nacido , Hígado/crecimiento & desarrollo , Hígado/metabolismo , Microsomas Hepáticos/enzimología , Microsomas Hepáticos/metabolismo , Oxidación-Reducción , Procesamiento Proteico-Postraduccional/fisiología , Sulfonamidas/análisis , Sulfonamidas/química

RESUMEN

AIMS: Cisapride has been shown to cause QTc prolongation in neonates in the absence of any of the known risk factors ascribed to children or adults (excessive dosage, drug-drug interactions). Our hypothesis was that the early neonatal liver may show defective elimination of cisapride resulting in its accumulation in the immature child. Owing to the difficulties associated with in vivo pharmacokinetic studies in a paediatric population, we explored the in vitro metabolism of cisapride by human cytochrome P450. METHODS: Experiments were conducted with recombinant CYPs stably expressed in mammalian cells and with liver microsomes obtained from human foetuses, neonates, infants and adults. Cisapride metabolites were measured by high performance liquid chromatography. RESULTS: The rate of biotransformation of cisapride was greater by recombinant CYP3A4 than by CYP3A7 (0.77 +/- 0.5 and 0.01 +/- 0.01 nmol metabolites formed in 24 h, respectively), whereas CYP1A1, 1A2, 2C8, 2C9 and 3A5 showed no activity. Norcisapride formation was significantly correlated with testosterone 6beta-hydroxylation, a CYP3A4 catalysed reaction (r = 0.71, P = 0.03) but not with the 16-hydroxylation of dehydroepiandrosterone, catalysed by CYP3A7 (r = 0.30, P = 0.29) by microsomes from a panel of livers from foetuses, neonates and infants. No or negligible cisapride metabolic activity was observed in microsomes from either foetuses or neonates aged less than 7 days, which contained mostly CYP3A7 and no CYP3A4. The metabolism of cisapride steadily increased after the first week of life in parallel with CYP3A4 activity to reach levels exceeding adult values. CONCLUSIONS: The low content of CYP3A4 in the human neonatal liver appears to be responsible for its inability to oxidize cisapride and could explain its accumulation in plasma leading to the cases of QTc prolongation reported in this paediatric population.

Asunto(s)

Cisaprida/metabolismo , Fármacos Gastrointestinales/metabolismo , Microsomas Hepáticos/metabolismo , Adulto , Biotransformación , Niño , Cromatografía Líquida de Alta Presión , Cisaprida/farmacocinética , Citocromo P-450 CYP3A , Sistema Enzimático del Citocromo P-450/metabolismo , Feto/metabolismo , Fármacos Gastrointestinales/farmacocinética , Humanos , Recién Nacido , Microsomas Hepáticos/enzimología , Oxigenasas de Función Mixta/metabolismo

RESUMEN

The ontogenesis of CYP1A proteins was investigated in a human liver bank composed of fetal, neonatal and adult samples. In immunoblots, a polyclonal antibody raised against rat CYP1A1, cross-reacted with cDNA-expressed human CYP1A1 and CYP1A2. In adult liver microsomes, this antibody reacted with a single band identified as the CYP1A2 protein, while no CYP1A1 could be detected. CYP1A2 protein was absent in microsomes prepared from fetal and neonatal livers and its levels increased in infants aged 1-3 months to attain 50% of the adult value at one year. Enzymatic activities supported by CYP1A proteins were assayed on these samples. Methoxyresorufin demethylase supported by the CYP1A2 recombinant protein followed the same ontogenic profile as the CYP1A2 protein. In liver microsomes, the demethylation of imipramine was essentially due to CYP1A2 and to a smaller extent to CYP3A. In fetuses and early neonates, CYP3A proteins were responsible for the low demethylation of imipramine (3-4% of the adult activity) before the onset of CYP1A2 and the subsequent rise of activity. Immunodetection and enzymatic activities were consistent with the absence of CYP1A1 and the late expression of CYP1A2 in the human liver, compared to the early rise of CYP3A4, CYP2C, CYP2D6, and CYP2E1 proteins.

Asunto(s)

Citocromo P-450 CYP1A2/biosíntesis , Sistema Enzimático del Citocromo P-450/biosíntesis , Regulación del Desarrollo de la Expresión Génica , Regulación Enzimológica de la Expresión Génica , Hígado/crecimiento & desarrollo , Microsomas Hepáticos/enzimología , Adulto , Envejecimiento/metabolismo , Animales , Células COS , Línea Celular , Citocromo P-450 CYP1A2/metabolismo , Sistema Enzimático del Citocromo P-450/metabolismo , Feto , Humanos , Lactante , Recién Nacido , Hígado/embriología , Ratas , Proteínas Recombinantes/biosíntesis , Especificidad por Sustrato , Transfección

RESUMEN

CYP3A isoforms are responsible for the biotransformation of a wide variety of exogenous chemicals and endogenous steroids in human tissues. Two members of the CYP3A subfamily display developmentally regulated expression in the liver; CYP3A7 is expressed in the fetal liver, whereas CYP3A4 is the major cyrochrome P-450 isoform present in the adult liver. To gain insight into the descriptive ontogenesis of CYP3A isoforms during the neonatal period, we have developed several approaches to explore a neonatal liver bank. Although CYP3A4 and CYP3A7 are structurally closely related, they differ in their capacity to carry out monooxygenase reactions. We have cloned CYP3A4 and CYP3A7 and established stable transfectants in Ad293 cells to investigate their substrate specificities. The 16alpha hydroxylation of dehydroepiandrosterone is catalyzed by both proteins, but CYP3A7 has a higher affinity and maximal velocity than CYP3A4. Conversely, the conversion of testosterone into its 6beta derivative is essentially supported by CYP3A4. We used these two probes to determine the ontogenic evolution at the protein level; CYP3A7 was very active in the fetal liver and its activity was maximal during the first week following birth before to progressively decline and reached a very low level in adult livers. Conversely, the activity of CYP3A4 was extremely weak in the fetus and began to raise after birth to reach 30-40% of the adult activity after one month. CYP3A4 RNA accumulation displays a similar pattern of evolution; when probed with an oligonucleotide, its concentration increased rapidly after birth to reach a plateau as soon as the first week of age. These data supports the assumption that CYP3A4 expression is transcriptionally activated during the first week after birth and is accompanied by a simultaneous decrease of CYP3A7 expression, in such a way that the overall CYP3A protein content and the level of pentoxyresorufin dealkylase catalyzed by the two proteins remain nearly constant.

Asunto(s)

Envejecimiento/metabolismo , Hidrocarburo de Aril Hidroxilasas , Sistema Enzimático del Citocromo P-450/biosíntesis , Regulación del Desarrollo de la Expresión Génica , Hígado/embriología , Hígado/crecimiento & desarrollo , Microsomas Hepáticos/enzimología , Oxigenasas de Función Mixta/biosíntesis , Adulto , Animales , Células COS , Línea Celular , Niño , Preescolar , Clonación Molecular , Citocromo P-450 CYP2C8 , Citocromo P-450 CYP2C9 , Citocromo P-450 CYP3A , Sistema Enzimático del Citocromo P-450/metabolismo , Desarrollo Embrionario y Fetal , Femenino , Feto , Regulación Enzimológica de la Expresión Génica , Edad Gestacional , Humanos , Lactante , Recién Nacido , Oxigenasas de Función Mixta/metabolismo , Embarazo , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/metabolismo , Esteroide 16-alfa-Hidroxilasa , Especificidad por Sustrato , Transcripción Genética , Transfección

RESUMEN

Experiments were performed in vivo and in vitro to date the onset of hepatic CYP2C isoforms and CYP2C-dependent activities during the perinatal period in humans. Proteins were not detected by immunoblotting in fetal livers and developed in the first few weeks after birth, irrespective of the gestational age at birth. Similarly, the hydroxylation of tolbutamide, a marker for CYP2C9 was undetected in fetal liver microsomes and rose in the first month after birth. In adult liver preparations, the hydroxylation of diazepam correlated well with the CYP3 A content of microsomes (r = 0.858, p < 0.01) and with the 6 beta hydroxylation of testosterone (r = 0.830, p < 0.005), whereas demethylation was related to the bulk of CYP2C proteins (r = 0.865, p < 0.005). In fetal liver microsomes, hydroxylation and demethylation activities accounted for less than 5% of the adult activities and both increased immediately after birth to reach adult activities at 1 year of age. When diazepam was given for sedative purpose in neonates and infants, the in-vivo urinary excretion of desmethyl diazepam, temazepam and oxazepam was extremely low in 1-2 day newborns (less than 5 nmol metabolites excreted in 24 h per kg body weight) and developed in the first week after birth. In newborns, barbiturates and to a lesser extent steroids, acted as inducers of CYP2C isoforms and increased tolbutamide hydroxylation, diazepam demethylation and diazepam hydroxylation by 2 to 10-fold. The surge of CYP2C proteins was caused by an accumulation of RNAs occurring in the first week after birth. The hepatic content in CYP2C8, 2C9 and 2C18 RNA displayed the same profile of evolution, which suggested a coregulation of their synthesis during the neonatal period. Taken together, these biochemical and clinical data enable dating of the onset of CYP2C proteins to the first weeks after birth, which is of considerable clinical importance in pediatric pharmacology.

Asunto(s)

Envejecimiento/metabolismo , Sistema Enzimático del Citocromo P-450/biosíntesis , Sistema Enzimático del Citocromo P-450/metabolismo , Microsomas Hepáticos/enzimología , Adulto , Envejecimiento/genética , Preescolar , Sistema Enzimático del Citocromo P-450/genética , Diazepam/metabolismo , Inducción Enzimática/genética , Inducción Enzimática/fisiología , Femenino , Feto , Edad Gestacional , Humanos , Hidroxilación , Lactante , Recién Nacido , ARN/biosíntesis , Tolbutamida/metabolismo

RESUMEN

In the human liver, the major rise of the cytochrome P-450 isoform content occurs during the first months following birth (e.g., the high vulnerability period to sudden infant death syndrome (SIDS), a syndrome frequently associated with viral infection and drug hypersensitivity. We examined the expression of individual P-450 isoforms in liver samples collected postmortem from SIDS infants and compared values with those of control adults and children of the same age suffering from various pathologies. Hepatic microsomes were prepared and examined for their content in total P-450, the level of individual isoforms (CYP1A2, CYP2E1, CYP4A, CYP3A, and CYP2C) determined with specific antibodies and for their enzymatic activities. Total RNA was extracted and probed with several CYP cDNAs and oligomers. The overall hepatic P-450 content was not modified in SIDS infants. Among cytochrome P-450 isoforms, only CYP2C was markedly increased. This rise resulted from an accumulation of RNA encoding CYP2C and was associated with a stimulation of diazepam demethylation. The precocious expression of CYP2C in SIDS could result in a higher production of epoxyeicosatrienoic acids in the neonate, believed to act as relaxant of pulmonary smooth muscles. Its consequence might be the induction of fatal apnea in SIDS.

Asunto(s)

Sistema Enzimático del Citocromo P-450/genética , Muerte Súbita , Hígado/química , Secuencia de Bases , Western Blotting , Expresión Génica/genética , Humanos , Lactante , Recién Nacido , Datos de Secuencia Molecular

RESUMEN

Cytochromes P-450 are responsible for the biotransformation of drugs and other hydrophobic molecules by the liver. Several isoforms coexist which display an asynchronous onset during the perinatal period suggesting the involvement of multiple mechanisms of regulation. In this paper, we have shown that the CYP2E1 protein and its associated activity could not be detected in the fetal liver and rise during the first few hours following birth independently of the gestational age (between 25-40 weeks). During this period, the CYP2E1 RNA content remains fairly low: the stabilization of the low amount of existing CYP2E1 protein by endogenous ketone bodies could explain the early neonatal rise of the protein level. From 1 month to 1 year, the protein content gradually increases and is accompanied by the accumulation of CYP2E1 RNA, suggesting a transcriptional activation of the gene during the late neonatal period. We examined the methylation status of CpG residues in the 5' flanking region, first exon and first intron of CYP2E1 gene cleaved with HpaII/MspI. Genomic DNA from fetal liver shows several hypermethylated spots in the first-exon-first-intron region, which progressively disappear in neonatal samples. We conclude that during the neonatal period, the accumulation of hepatic CYP2E1 RNA is correlated with the degree of methylation at the 5' end of the CYP2E1 gene.

Asunto(s)

Sistema Enzimático del Citocromo P-450/biosíntesis , Sistema Enzimático del Citocromo P-450/genética , Regulación del Desarrollo de la Expresión Génica , Hígado/metabolismo , Oxidorreductasas N-Desmetilantes/biosíntesis , Oxidorreductasas N-Desmetilantes/genética , Adulto , Envejecimiento , Secuencia de Bases , Southern Blotting , Clorzoxazona/metabolismo , Citocromo P-450 CYP2E1 , Sondas de ADN , Feto/enzimología , Edad Gestacional , Humanos , Hidroxilación , Lactante , Recién Nacido , Hígado/embriología , Hígado/crecimiento & desarrollo , Metilación , Microsomas Hepáticos/metabolismo , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , ARN Mensajero/análisis , ARN Mensajero/metabolismo , Mapeo Restrictivo

RESUMEN

The metabolism of docetaxel by human liver microsomes was investigated in vitro and compared with that of paclitaxel. A main docetaxel metabolite was generated by human liver microsomes in the presence of NADPH: retention time in high pressure liquid chromatography and its ion fragmentation in mass spectrometry were identical to those of the authentic derivative hydroxylated at the butyl group of the C13 side chain. Kinetic measurements and chemical and immunological inhibitions demonstrated that CYP3A was implicated in the hydroxylation of docetaxel: Km (2 microM) and Vm values of docetaxel for human liver microsomes were comparable to those calculated for the formation of metabolite p-hydroxy-phenyl C3' paclitaxel (M4). Docetaxel hydroxylation correlated only with the CYP3A content of microsomes and with CYP3A-dependent 6 beta-hydroxylation of testosterone and 16-hydroxylation of dehydroepiandrosterone. The formation of hydroxydocetaxel was strongly reduced by CYP3A inhibitors such as ketoconazole, midazolam, erythromycin, testosterone, orphenadrine, and troleandomycin, whereas quinidine (CYP2D6), hexobarbital, tolbutamide, and mephenytoin (CYP2C) had no or little effect. The hydroxylation of docetaxel exhibited a highly positive correlation with the formation of metabolite M4 of paclitaxel (r = 0.929, P < 0.0001, n = 12), but not with its 6-hydroxylation (r = 0.48, P > 0.15). Docetaxel abolished the hydroxylation of paclitaxel metabolite M4, but was totally inactive on its 6 alpha-hydroxylation. Conversely, paclitaxel reduced significantly the hydroxylation of docetaxel. We examined in vitro the possible interaction among docetaxel, paclitaxel, and drugs which could be associated during chemotherapy. Cisplatin, verapamil, doxorubicin, vinblastine, and vincristine at concentrations usually recommended did not markedly modify taxoid metabolism. Ranitidine and diphenylhydramine had no effect, but 100 microM cimetidine partially inhibited the formation of 6 alpha-hydroxypaclitaxel. Pretreatment of patients with barbiturates strikingly stimulated docetaxel hydroxylation, whereas no acceleration of docetaxel hydroxylation was noticed in a patient receiving steroids.

Asunto(s)

Antineoplásicos Fitogénicos/metabolismo , Sistema Enzimático del Citocromo P-450/metabolismo , Isoenzimas/metabolismo , Microsomas Hepáticos/metabolismo , Paclitaxel/análogos & derivados , Paclitaxel/metabolismo , Taxoides , Docetaxel , Femenino , Humanos , Hígado/embriología , Hígado/metabolismo , Embarazo

RESUMEN

A cytochrome P-450 N (N for Neonatal) was resolved and partially purified from 15-day-old newborn rat livers. Antibody raised in rabbit against P-450 N detects two bands in liver microsomes, the major one comigrating with the partially purified P-450 N. This protein is not expressed in lung and kidney and exhibits an unusual ontogenic profile in the liver with maximal levels in 2-week-old animals. Expression of P-450 N is not modified in animals given beta-naphthoflavone or pregnenolone 16 alpha-carbonitrile, but is markedly increased by phenobarbital. Its amino-acid composition differs from that of other P-450s and it is not recognized by antibodies directed against CYP1A, CYP2A1, CYP2B, CYP2C11, CYP3A or epoxide hydrolase. It could thus be considered as an unique P-450 expressed transiently before puberty.

Asunto(s)

Animales Recién Nacidos/metabolismo , Sistema Enzimático del Citocromo P-450/metabolismo , Secuencia de Aminoácidos , Animales , Benzoflavonas/farmacología , Western Blotting , Sistema Enzimático del Citocromo P-450/aislamiento & purificación , Electroforesis en Gel de Poliacrilamida , Femenino , Riñón/enzimología , Hígado/crecimiento & desarrollo , Pulmón/enzimología , Masculino , Microsomas Hepáticos/enzimología , Datos de Secuencia Molecular , Fenobarbital/farmacología , Carbonitrilo de Pregnenolona/farmacología , Ratas , Ratas Sprague-Dawley , beta-naftoflavona

RESUMEN

Several in vitro studies have shown that the cyclin A gene is expressed and plays an important role in both the S and G2-M phases of the cell cycle. We analyzed cells from the blood and bone marrow of patients with various, mostly neoplastic, hematological disorders to determine whether (a) the cyclin A protein level correlated with that of cyclin A RNA and (b) cell distribution among the different phases of the cell cycle correlated with cyclin A RNA expression. Thirty-eight patients were studied by means of dot blot and Western blot techniques for cyclin A RNA and protein accumulation, and 21 were also studied for cell cycle distribution by using flow cytometric analysis. Semiquantitative studies were based on densitometric computerized evaluation of dot and Western blots. There was a very strong positive correlation between cyclin A RNA and protein expression (r = 0.99; P < 0.00005), indicating that cyclin A accumulation is regulated in these cells at a transcriptional level. There was also a highly significant positive correlation between cyclin A RNA expression and the cumulative percentage of cells in S plus G2-M phase (r = 0.98; P < 0.00005). Therefore, this in vivo study shows that the expression of cyclin A RNA and protein in human hematological malignancies correlates with the percentage of cells in S plus G2-M phase and identifies cyclin A as a new potential cell proliferation index in oncology.

Asunto(s)

División Celular , Ciclinas/genética , Leucemia/patología , Linfoma/patología , Ciclo Celular , Ciclinas/metabolismo , Expresión Génica , Humanos , Leucemia/diagnóstico , Linfoma/diagnóstico , ARN Mensajero/genética , ARN Neoplásico/genética

RESUMEN

p-125I-amphetamine (I-Amp) is retained significantly in liver and lung during brain tomoscintigraphy. To attempt to explain this clinical observation, we have investigated the interaction of I-Amp with rat liver and lung microsomal proteins. Studies using spectral shift technique indicate that low concentration of I-Amp gives a type I complex and high concentration appears very stable type II complex with cytochrome P-450 Fe III. In the presence of NADPH, I-Amp gives rise to a 455 nm absorbing complex with similar properties to the Fe-RNO complexes. This complex formation was greatly enhanced with phenobarbital treated liver microsomes. The in vitro binding study shows that I-Amp and/or its metabolites was covalently bound to macromolecules in the presence of the molecular oxygen and NADPH-generating system. Incubation in the presence of glutathione, cystein and radical scavengers decreases binding. Mixed function oxydase (MFO) inhibitors diminish the amount of covalent binding and alter the extent of metabolite formation. The total covalent binding level increased with liver microsomes from PB pretreated rats as it was observed with the 455nm complex formation. The radioactivity distribution on microsomal proteins was examinated with SDS polyacrylamide gel electrophoresis and autoradiography. This experiment proves that the radiolabelled compounds are bound on the cytochrome P-450. The radioactivity bound increased when the PB induced rat liver microsomes were used. All these results indicate that I-Amp was activated by an oxydative process dependent on the MFO system which suggests a N-oxydation of I-Amp and the formation of reactive entities which covalently bind to proteins.

Asunto(s)

Anfetamina/metabolismo , Radioisótopos de Yodo/metabolismo , Pulmón/metabolismo , Microsomas Hepáticos/metabolismo , Microsomas/metabolismo , Animales , Sistema Enzimático del Citocromo P-450/metabolismo , Pulmón/ultraestructura , Masculino , Unión Proteica , Ratas , Ratas Endogámicas

RESUMEN

To explore the possibility of liver enzyme induction by deltamethrin, subacute intoxication was carried out in rats for 28 days, by administration 7.2 mg.Kg-1.day-1 of deltamethrin i.p. delivered by an osmotic pump inserted in the peritoneal cavity. The body weight curve of the treated rats increased slightly but not significantly compared to the controls. No neurotoxic effect was observed. Blood parameters were unchanged, except for eosinophilia and an increase in the plasma Na+ level. Cytochrome P-450, cytochrome b5, NADPH-cytochrome c reductase, esterases and the activities of six mixed function oxidases were assayed. No variation was noted. Ultrastructural study of the liver, more specially in midlobular region, showed that deltamethrin increased the number of mitochondria and altered their shape which became irregular. These findings were consistent with morphometric results. Succinate cytochrome c reductase, citrate synthase and cytochrome c oxidase were essayed, only this last showed a significant enhancement in deltamethrin treated rats.

Asunto(s)

Insecticidas/toxicidad , Piretrinas/toxicidad , Animales , Peso Corporal/efectos de los fármacos , Femenino , Pruebas Hematológicas , Bombas de Infusión , Insecticidas/administración & dosificación , Hígado/ultraestructura , Microsomas Hepáticos/enzimología , Mitocondrias Hepáticas/enzimología , Nitrilos , Presión Osmótica , Piretrinas/administración & dosificación , Ratas , Ratas Endogámicas , Sodio/sangre

RESUMEN

Phenobarbital-induced rat liver homogenate and microsomes were used to study covalent binding of 14C-labelled (at the alcohol moiety) cismethrin, 14C-labelled (at the alcohol and acid moieties) cypermethrin, and 14C-labelled (at the alcohol and acid moieties) deltamethrin. Covalent binding was dependent on pyrethroid concentration. With liver homogenate, inhibition of esterases by tetraethylpyrophosphate and of mitochondrial respiration by rotenone or potassium cyanide only slightly altered the covalent binding level. With microsomes, inhibition of cytochrome P-450 and mixed function oxidases by carbon monoxide and piperonyl butoxide reduced the covalent binding so far as to be nearly absent. Eighty percent inhibition of epoxide hydrolase decreased the covalent binding by 50%. The comparison of data between alcohol and acid labelling of the same pyrethroid suggested that, in vitro, the whole molecule is bound to proteins and that hydrolysis can occur afterwards. The experiments stress the role of cytochrome P-450-dependent monoxygenases in the covalent binding process.

Asunto(s)

Insecticidas/metabolismo , Hígado/metabolismo , Microsomas Hepáticos/metabolismo , Piretrinas/metabolismo , Animales , Inhibidores Enzimáticos , Femenino , Técnicas In Vitro , Hígado/enzimología , Microsomas Hepáticos/enzimología , Nitrilos , Unión Proteica , Piretrinas/farmacología , Ratas , Ratas Endogámicas

RESUMEN

Pyrethroids are potent synthetic insecticides which have been increasingly employed in recent years. Such compounds have been shown to bind covalently to hepatic proteins. Covalent binding is often associated with toxic effects. Possible cytotoxic, cytogenotoxic and allergenic effects could be due to covalent binding of these compounds and/or their metabolites to endogenous macromolecules. In the present paper we examine possible cytotoxic effects of certain pyrethroids on human lymphocytes and L 1210 lymphoblastoid mouse cells, cytogenotoxic effects with micronuclei test and allergenic effects with Magnusson and mast cell degranulation tests. Under our experimental conditions, the tested compounds showed neither acute cytotoxic nor cytogenotoxic effects, though, Cismethrin presented slight antimitotic effects statistically different to those with the control. Slight allergenic character of Cismethrin, Bioresmethrin and Deltamethrin was revealed by Magnusson and mast cell degranulation tests.

Asunto(s)

Insecticidas/farmacología , Linfocitos/efectos de los fármacos , Piretrinas/farmacología , Células Tumorales Cultivadas/efectos de los fármacos , Animales , Supervivencia Celular/efectos de los fármacos , Humanos , Leucemia L1210 , Mastocitos/efectos de los fármacos , Ratones , Nitrilos , Permetrina , Ratas , Ratas Endogámicas

RESUMEN

When [14C]Alcohol-labeled cismethrin, bioresmethrin, and 5-benzyl-3-furylmethyl alcohol (BFA) were incubated with rat liver S 9 homogenates or microsomes, a proportion of the radioactive compounds was covalently bound to proteins. The covalent binding was greater with phenobarbital-pretreated rats, and dependent on a NADPH-generating system. When a S 9 homogenate was used, the bound compounds were twofold higher for cismethrin than for bioresmethrin and BFA. Inversely, when microsomes were used more covalent binding occurred with bioresmethrin and BFA than with cismethrin. The inhibition of esterases by tetraethyl pyrophosphate (TEPP) in a S 9 homogenate did not alter the amount of covalent binding to the three compounds whereas malathion inhibited this binding. Treatment of a S 9 homogenate with piperonyl butoxide, however, greatly reduced covalent binding. Covalent binding was inhibited when the microsomes were incubated with carbon monoxide or modified by thermal denaturation. It is suggested that oxidative metabolism was responsible for the covalent binding.

Asunto(s)

Hígado/metabolismo , Piretrinas/metabolismo , Animales , Radioisótopos de Carbono , Hidrolasas de Éster Carboxílico/antagonistas & inhibidores , Sistema Enzimático del Citocromo P-450/metabolismo , Interacciones Farmacológicas , Electroforesis , Femenino , Hígado/efectos de los fármacos , Malatión/farmacología , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Oxigenasas de Función Mixta/antagonistas & inhibidores , NADP/metabolismo , Compuestos Organofosforados/farmacología , Butóxido de Piperonilo/farmacología , Ratas , Ratas Endogámicas

RESUMEN

The covalent binding level of [14C]alcohol-labelled cismethrin, bioresmethrin and/or their metabolites to hepatic proteins was measured after a single i.v. injection of pyrethroids in rats pretreated with malathion. In the first control group, the radiolabel binding level was different for cismethrin (35.3 pmol X mg-1 protein) and bioresmethrin (22.6 pmol X mg-1 protein) and in the treated rats, the amount of binding was reduced similarly for the two pyrethroids (13 pmol X mg-1 protein). After 13 days of chronic i.p. treatment, the covalent binding level on microsomal protein was 3 times higher for cismethrin than for bioresmethrin and the ratio of cismethrin to bioresmethrin covalent binding level was similar to that after a single i.v. injection. It is suggested that the difference in covalent binding distribution and concentration in the various subcellular fractions of liver was due to the different routes of metabolism of the two resmethrin isomers.

Asunto(s)

Hígado/metabolismo , Piretrinas/metabolismo , Animales , Femenino , Malatión/farmacología , Unión Proteica , Ratas , Ratas Endogámicas , Factores de Tiempo

Asunto(s)

Cannabinoides/orina , Cromatografía/métodos , Cromatografía Liquida/métodos , Cromatografía en Capa Delgada/métodos , Cromatografía de Gases y Espectrometría de Masas/métodos , Humanos

RESUMEN

Gas chromatography was used in blood samples for determining human exposure to organophosphate insecticides. The identification is difficult beyond 48 hr after exposure because of the high reactivity of these compounds.

Asunto(s)

Insecticidas/sangre , Compuestos Organofosforados , Enfermedades de los Trabajadores Agrícolas/inducido químicamente , Colinesterasas/sangre , Cromatografía de Gases , Eritrocitos/enzimología , Humanos , Insecticidas/envenenamiento , Métodos

RESUMEN

Here is an attempt to establish that a close relation exists between the chemical formulae of organophosphates and their affinities for lipids, proteins and water. We carried out this study on two systems similar to human plasma. First, each component was sorted, then the organophosphates were detected and titrated by gas chromatography with flame photometry detector. Thiophosphates had a greater affinity for lipids than phosphates. Fixation of proteins was only observed on three hydrophilous organophosphates: phosphamidon, dichlorvos, ciodrin.

Asunto(s)

Insecticidas/sangre , Compuestos Organofosforados , Sustitutos del Plasma/análisis , Fenómenos Químicos , Química , Cromatografía de Gases , Lípidos/sangre , Compuestos Organotiofosforados , Unión Proteica , Albúmina Sérica/metabolismo , Solubilidad , Relación Estructura-Actividad , Agua

RESUMEN

The hydroxyimino-1 methyl-4 pentanone-2 was selected among several oximes because of its highly successful restoring action on dog plasmatic cholinesterases inhibited by DFP (diisopropyl fluorophosphate). During the in vitro study, this storing action was tested on 10 organophosphates. Results are compared to those obtained when contrathion is used.

Asunto(s)

Reactivadores de la Colinesterasa/farmacología , Colinesterasas/sangre , Insecticidas/farmacología , Oximas/farmacología , Animales , Perros , Activación Enzimática/efectos de los fármacos , Isoflurofato/farmacología , Factores de Tiempo