RESUMEN

BACKGROUND: Sepsis is common in neonates and a major cause of morbidity and mortality. Sixty percent of preterm neonates receive at least one antibiotic during the first week of life, with penicillins being the most frequently administered antibiotics. The clearance (Cl), serum half-life (t((1/2))) and volume of distribution (Vd) of penicillins are different in the neonate than in the adult. As such, the pharmacokinetics of penicillins need be studied in neonates in order to optimise therapy in this age class with these drugs. OBJECTIVES: The aim of this study was to review the published data on the pharmacokinetics of penicillins in the neonate in order to provide a critical analysis of the literature and, consequently, a useful tool in the hands of the physician. METHODS: The bibliographic search was performed electronically using the PubMed and EMBASE databases as search engines. An initial search was performed with the keywords "pharmacokinetics", "penicillins" and "neonates". Secondly, other searches were performed using the keywords "pharmacokinetics" and "neonates", followed by the name of a single antibiotic. The search included articles up to 2007. RESULTS: There have been few pharmacokinetic studies on the use of penicillins in neonates. The results from those few studies that have been carried out suggest that the Cl is reduced and t((1/2)) prolonged in the neonate as compared with the more mature infant. There is little variation in Vd during the first week of life. In the premature neonate, Cl is reduced compared to the full-term infant. As postnatal age proceeds, the Cl of penicillins increases. CONCLUSIONS: More pharmacokinetic studies are required to provide a sound scientific basis for planning a dosage regimen with penicillins in the neonate.

Asunto(s)

Antibacterianos/farmacocinética , Penicilinas/farmacocinética , Antibacterianos/química , Antibacterianos/uso terapéutico , Competencia Clínica , Humanos , Recién Nacido , Penicilinas/química , Penicilinas/uso terapéutico , Médicos

RESUMEN

BACKGROUND: The purpose of antibiotic treatment in pregnant women is to treat the mother and/or the fetus since it is known that antibiotics administered to the mother cross the placenta and reach the fetus. A comparison of the drug concentration in maternal and fetal plasma gives an indication of the exposure of the fetus to the maternally administered antibiotics. AIM: The aim of this study was to review the literature pertaining to the placental transfer of antibiotics in man and to classify the antibiotics according to the type of transfer involved. A table has been developed for use by physicians that lists the name of the antibiotic, the drug concentration in the cord and maternal plasma at delivery and the type of transfer involved. METHODS: An initial medline search was performed with the key words "placental transfer of antibiotics" with the limit of "human". A second medline search was performed with the key words "placental transfer of..." followed by the class names of the antibiotic such as penicillins, cephalosporins, aminoglycosides, tetracyclines and macrolides. The bibliographic search on the placental transfer of antibiotics covered the period up to July 2005. RESULTS: 3 types of placental transfers were identified. A few antibiotics cross the placenta rapidly and equilibrate in the maternal and cord plasma; this type of transfer is termed "complete" and include the antibiotics ampicillin, methicillin, cefmenoxime and cefotiam. Antibiotics which show incomplete transfer to the placenta where concentrations are lower in the cord than maternal plasma are said to have "incomplete" transfer and these include azlocillin, dicloxacillin, piperacillin, sulbenicillin, cefoxitin, amikacin, gentamicin, kanamycin, streptomycin, fosfomycin, thiamphenicol, griseofulvin, vancomycin and colistimethate. Ceftizoxime is the only antibiotic so far known whose concentrations are higher in the cord than maternal plasma. This type of transfer is called "exceeding" transfer. CONCLUSION: All examined antibiotics cross the human placenta including those with a molecular weight greater than 1000 kDa such as vancomycin and colistimethate but there are 3 distinct types of placental transfer: complete, incomplete and exceeding and most antibiotics exhibit incomplete transfer.

Asunto(s)

Antibacterianos/farmacocinética , Intercambio Materno-Fetal/fisiología , Placenta/fisiología , Antibacterianos/sangre , Relación Dosis-Respuesta a Droga , Femenino , Sangre Fetal/metabolismo , Humanos , Embarazo

RESUMEN

Human sulfotransferases catalyze sulfate conjugation and 2 polymorphic genes, SULT1A1 and SULT1A2 in this family of transferases have been identified, encoding for 2 isoenzymes with very similar properties and substrate specificities. In order to test the hypothesis that variability in sulfation is due to genetic polymorphism in SULT1A1, the sulfation rate of 4-nitrophenol, a diagnostic substrate, was measured in 50 human liver samples and the genotype at the SULT1A1 locus was analyzed. The rate of 4-nitrophenol sulfation varied from 473 - 1,405 pmol/min/mg between the 5th and 95th percentiles, with a median and a mean +/- SD of 757 and 807 +/- 292 pmol/min/mg, respectively. The activities detected among the SULT1A1*2/*2 homozygotes (5 cases) were significantly lower than those of the other 2 genotypes, SULTA1*11/*1 and SULT1A1*1/*2 (5 and 40 cases, respectively), whereas there was no significant difference found between the SULT1A1*1/*1 and SULT1A1*1/*2 genotypes. To evaluate the possible influence of SULT1A2 polymorphism, genotype assays were also performed for this locus. No SULT1A2*2/*2 carrier, 26 SULT1A2*1/*1 and 24 SULT1A2*1/*2 were detected in the population sample under study. However, no correlation between the rate of 4-nitrophenol sulfation and the SULT1A2 genotype was detected. These results confirm that the variation in the rate of 4-nitrophenol sulfation in human liver is mainly due to SULT1A. Since SULT1A1*1/*2 polymorphism accounts for no more than 10% of the phenotypic variation seen in this cohort, other factors must also contribute to the variability in the rate of 4-nitrophenol sulfation in human liver. However, on the basis of the data obtained, variations in age, gender and liver function as possible causative factors can be excluded. The IC50 of quercetin, a potent inhibitor of 4-nitrophenol sulfation, was measured in the liver samples and ranged from 4.6 to 17.3 nM between the 5th and 95th percentiles. The median and the mean +/- SD were 7.7 nM and 8.3 +/- 2.5 nM, respectively. There was a weak but significant correlation between the IC50 value and age of the liver donors (r = 0.283, p = 0.046). The observed variation did not correlate with the genotypes at the SULT1A1 and SULT1A2 loci.

Asunto(s)

Arilsulfotransferasa/antagonistas & inhibidores , Hígado/metabolismo , Quercetina/farmacología , Adulto , Anciano , Anciano de 80 o más Años , Arilsulfotransferasa/genética , Inhibidores Enzimáticos/farmacología , Femenino , Genotipo , Humanos , Técnicas In Vitro , Concentración 50 Inhibidora , Hígado/enzimología , Masculino , Persona de Mediana Edad , Nitrofenoles/metabolismo , Nitrofenoles/normas , Fenotipo , Fosfoadenosina Fosfosulfato/metabolismo , Polimorfismo Genético

RESUMEN

Sulfotransferase catalyzes the transfer of sulfate, donated by 3'-phosphoadenosine-5'-phosphosulfate, to an acceptor substrate that may be a hydroxy group or an amine group. Man is exposed daily to drugs and dietary chemicals that can inhibit sulfotransferase activity. The aim of this study was to review the literature concerning the inhibition of sulfotransferases by drugs and dietary chemicals in the human liver and duodenum. The IC50 value of mefenamic acid for human liver phenol sulfotransferase (SULT 1A1) was 0.02 microM and for human liver catechol sulfotransferase (SULT1A3) 76 microM with a SULT 1A3/SULT1A1 ratio for the IC50 of 3,800. Mefenamic acid is therefore a potent and selective inhibitor of human liver SULT1A1. The IC50 values of mefenamic acid for the sulfation rates of (-)-salbutamol and (-)-apomorphine were 4 orders of magnitude greater in the human duodenum than in the liver. Salicylic acid inhibited the sulfation of (-)-apomorphine in human liver with an IC50 of 54 gM but did not inhibit the sulfation of (-)-apomorphine in human duodenum. Quercetin, a flavonoid present in edible fruit, vegetable and wine, was a potent inhibitor of human liver SULT1A1 and estrogen sulfotransferase (EST) activities and the sulfation of resveratrol. Quercetin inhibited the sulfation of dopamine, (-)-salbutamol, minoxidil and paracetamol and the IC50 values were 1 - 2 orders of magnitude greater in human duodenum than in the liver. In conclusion, mefenamic acid, salicylic acid and quercetin inhibit SULT1A1 whereas SULT1A3 is relatively resistant to the inhibition by these compounds. Under particular circumstances, human duodenum sulfotransferase is more resistant than liver sulfotransferase to the inhibition by mefenamic acid, salicylic acid and quercetin.

Asunto(s)

Antiinflamatorios no Esteroideos/farmacología , Duodeno/efectos de los fármacos , Hígado/efectos de los fármacos , Sulfotransferasas/biosíntesis , Duodeno/enzimología , Humanos , Concentración 50 Inhibidora , Hígado/enzimología , Ácido Mefenámico/farmacología , Quercetina/farmacología , Ácido Salicílico/farmacología , Sulfotransferasas/antagonistas & inhibidores

RESUMEN

1. Curcumin has anti-carcinogen effects and is under clinical evaluation as a potential colon cancer chemopreventive agent. The first aim was to see whether curcumin inhibited phenol sulfotransferase (SULT1A1) and, if so, to study the variability of the IC(50) of curcumin for SULT1A1 in 50 human liver samples. For comparative purposes, the inhibition of catechol sulfotransferase (SULT1A3) in five human liver specimens was studied. The second aim was to measure the IC(50) of curcumin against SULT1A1 in five samples of human duodenum, colon, kidney and lung. 2. Curcumin was a potent inhibitor of SULT1A1 in human liver; the mean +/- SD and median of IC(50) were 14.1 +/- 7.3 nM and 12.8 nM, respectively. The IC(50) ranged from 6.2 to 30.6 nM between the 5th and 95th percentiles and the fold of variation was 4.9. The distribution of IC(50) was positively skewed (skewness 1.2) and deviated from normality (p = 0.0004). 3. Curcumin inhibited human SULT1A3, and the inhibition was studied in five liver specimens with an IC(50) of 4324 +/- 1026 nM. This inhibition was greater than the IC(50) of curcumin for SULT1A1 (p < 0.0001). 4. In the extrahepatic tissues, the IC(50) of curcumin for SULT1A1 was 25.9 +/- 4.8 nM (duodenum), 25.4 +/- 6.8 nM (colon), 23.4 +/- 2.2 nM (kidney) and 25.6 +/- 5.6 nM (lung). Inhibition in these tissues is greater than that of curcumin for SULT1A1 in human liver (p < 0.0001). 5. In conclusion, curcumin is a potent inhibitor of SULT1A1 in human liver, duodenum, colon, kidney and lung. The IC(50) of curcumin for SULT1A1 varied 4.9-fold in human liver. The comparison of the present data with those of the literature revealed that the IC(50) of curcumin in the liver and extrahepatic tissues is one order of magnitude lower that the peak serum concentration of curcumin after therapeutic doses of 4 g to humans.

Asunto(s)

Arilsulfotransferasa , Curcumina/farmacología , Inhibidores Enzimáticos/farmacología , Hígado/enzimología , Sulfotransferasas/antagonistas & inhibidores , Adulto , Citosol/enzimología , Femenino , Hepatectomía , Humanos , Isoenzimas/antagonistas & inhibidores , Isoenzimas/metabolismo , Pruebas de Función Hepática , Masculino , Sulfotransferasas/metabolismo

RESUMEN

The first aim of this investigation was to study the sulfation of R(-)-apomorphine in human brain. The second aim was to investigate the inhibition of R(-)-apomorphine sulfation by quercetin in human brain. R(-)-apomorphine is hereafter referred to as apomorphine. Apomorphine sulfation was measured in 5 brain specimens; 3 derived from the frontal cortex and 2 derived from the temporal cortex. The rate of apomorphine sulfation was 5.6 +/- 4.3 pmol/min/mg. The activities of SULT1A1 and SULT1A3, which were also measured in these samples, were 11 +/- 9.1 and 2.6 +/- 1.7 pmol/min/mg, respectively. The rate of apomorphine sulfation correlated with the activity of SULT1A1 (r = 0.989; p = 0.002) and SULT1A3 (r = 0.973; p = 0.005). Apomorphine sulfotransferase followed Michaelis-Menten kinetics, the Km (mean +/- SD) and Vmax values (mean +/- SD) of which, measured in 5 brain samples, were 32 +/- 7.3 microM and 8.9 +/- 7.9 pmol/min/mg, respectively. Quercetin was a potent inhibitor of apomorphine sulfation with an IC50 value, measured in 5 brain samples, of 16 +/- 2.3 nM. The inhibition mechanism of quercetin using apomorphine sulfation in 5 brain samples was mixed, non-competitive with a Ki and Kies (mean +/- SD) of 16 +/- 4.1 and 87 +/- 37 nM, respectively (p = 0.008). The intrinsic clearance value of apomorphine (mean +/- SD) was 247 +/- 170 ml/min/mg(-1) and was decreased to 100 +/- 85 ml/min/mg(-1) (p < 0.01) in the presence of 25 nM quercetin. In conclusion, apomorphine is sulfated in human brain. Sulfation might reduce the level of apomorphine in human brain and be a factor limiting the effect of this drug. Quercetin is a potent inhibitor of apomorphine sulfation and may inhibit the sulfation of apomorphine in human brain in vivo.

Asunto(s)

Apomorfina/metabolismo , Arilsulfotransferasa , Encéfalo/metabolismo , Agonistas de Dopamina/metabolismo , Quercetina/farmacología , Sulfotransferasas/metabolismo , Adulto , Anciano , Femenino , Humanos , Técnicas In Vitro , Cinética , Masculino , Persona de Mediana Edad

RESUMEN

1. The aim of this investigation was to see whether 7-OH-flavone, 5-OH-flavone and 3-OH-flavone, which are present in edible vegetables, fruit and wine, are substrates or inhibitors of human liver and duodenum sulfotransferase. 2. An assay was set up to study the sulfation of 7-OH-flavone, and using this assay, it was observed that 7-OH-flavone was sulfated and the rate of sulfation (mean +/- SD) was 324 +/- 87 pmol min(-1) mg(-1) (liver) and 584 +/- 164 pmol min(-1) mg(-1) (duodenum; p < 0.0001). 3. 7-OH-flavone sulfotransferase followed Michaelis-Menten kinetics and the K(m) (mean +/- SD) was 0.2 +/- 0.04 microM (liver) and 1.1 +/- 0.3 microM (duodenum; p = 0.008). V(max) (mean +/- SD) was 392 +/- 134 pmol min(-1) mg(-1) (liver) and 815 +/- 233 pmol min(-1) mg(-1) (duodenum; p = 0.016). 4. 5-OH-flavone and 3-OH-flavone were not sulfated and were inhibitors of human liver and duodenum SULT1A1 activity and 7-OH-flavone sulfation rate. 5. The IC50 of 5-OH-flavone for SULT1A1 was 0.3 +/- 0.06 microM (liver) and 0.3 +/- 0.1 microM (duodenum; n.s.) and those of 3-OH-flavone were 1.0 +/- 0.1 microM (liver) and 1.6 +/- 0.03 microM (duodenum; p = 0.0006). 6. There was inhibition of 7-OH-flavone sulfation rate by 5-OH-flavone and 3-OH-flavone. The IC(50) of 5-OH-flavone for the sulfation rate of 7-OH-flavone was 3.5 +/- 0.5 microM (liver) and 69 +/- 18 microM (duodenum; p < 0.0001) and for 3-OH-flavone it was 18 +/- 3.4 microM (liver) and 213 +/- 47 microM (duodenum; p < 0.0001). 7. The position of the hydroxy group confers to the molecules of OH-flavones the quality of substrate or inhibitor of sulfotransferase.

Asunto(s)

Arilsulfotransferasa , Duodeno/metabolismo , Flavonoides/metabolismo , Hígado/metabolismo , Sulfotransferasas/antagonistas & inhibidores , Adulto , Anciano , Anciano de 80 o más Años , Duodeno/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Femenino , Flavonoides/farmacología , Humanos , Técnicas In Vitro , Cinética , Hígado/efectos de los fármacos , Masculino , Persona de Mediana Edad , Especificidad por Sustrato , Sulfatos/metabolismo , Sulfotransferasas/metabolismo

RESUMEN

1. The aims were to study the sulfation of R-(-)-apomorphine (hereafter apomorphine) in the human liver and duodenum, and to study the rate of inhibition of apomorphine sulphation by mefenamic acid, salicylic acid and quercetin also in the human liver and duodenum. 2. A rapid and sensitive method was developed to measure the sulfation rate of apomorphine in the human liver and duodenum. The method was based on the use of 0.4 micro M 3'-phosphoadenosine-5'-phosphosulfate-[(35)S] (PAPS) and 50 micro M apomorphine. The unreacted PAPS was precipitated with barium hydroxide, barium acetate and zinc sulfate. 3. The rate of apomorphine sulfation (mean +/- SD and median) was 261 +/- 82 and 242 pmol min(-1) mg(-1), respectively (liver), and 433 +/- 157 and 443 pmol min(-1) mg(-1), respectively (duodenum). The apomorphine sulfation rate was higher in the duodenum than in the liver (p = 0.0005). 4. Apomorphine sulfation was correlated with SULT1A1 activity in the liver (r(2) = 0.363, p = 0.005) and duodenum (r(2) = 0.494, p = 0.0005), but it did not correlate with SULT1A3 activity both in the liver and duodenum. 5. The K(m) estimate of apomorphine sulfation rate was 20 +/- 3.6 (liver) and 6.5 +/- 0.2 microM (duodenum, p = 0.024), and the V(max) estimate was 248 +/- 99 (liver) and 636 +/- 104 pmol min(-1) mg(-1) (duodenum, p = 0.018). 6. Mefenamic acid, salicylic acid and quercetin were potent inhibitors of apomorphine sulfation rate in the liver, and the IC(50) estimates were 16 +/- 0.2 nM, 54 +/- 8.6 microM and 18 +/- 2.8 nM, respectively. These compounds were poor inhibitors of apomorphine sulfation in the duodenum. 7. Apomorphine is sulfated by the human liver and duodenum, the highest activity being associated with the duodenum. The K(m) of apomorphine sulfotransferase is in the order of micro M both in the liver and duodenum. The non-steroidal anti-inflammatory drug mefenamic acid and the natural flavonoid quercetin inhibit the hepatic sulfation of apomorphine with an IC(50) in the order of nM.

Asunto(s)

Apomorfina/metabolismo , Arilsulfotransferasa , Duodeno/metabolismo , Hígado/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Antiinflamatorios no Esteroideos/farmacología , Apomorfina/química , Duodeno/efectos de los fármacos , Femenino , Humanos , Técnicas In Vitro , Cinética , Hígado/efectos de los fármacos , Masculino , Ácido Mefenámico/farmacología , Persona de Mediana Edad , Quercetina/farmacología , Ácido Salicílico/farmacología , Estereoisomerismo , Sulfatos/metabolismo , Sulfotransferasas/antagonistas & inhibidores , Sulfotransferasas/metabolismo

RESUMEN

1. Quercetin is one of the most abundant flavonoids in edible vegetables, fruit and wine. The aim was to study the type of inhibition of SULT1A1 by quercetin in the human adult and foetal livers. 2. The activity of SULT1A1 was measured with 4 microM 4-nitrophenol and 0.4 microM 3'-phosphoadenosine-5'-phosphosulphate-[(35)S], and its mean (+/-SD) and median were 769 +/- 311 and 740 pmol min(-1) mg(-1), respectively (adult liver, n = 10), and 185 +/- 98 and 201 pmol min(-1) mg(-1), respectively (foetal liver, n = 8, p < 0.0001). 3. In non-inhibited samples, K(m) for SULT1A1 (mean +/- SD) was 0.31 +/- 0.14 microM (adult liver) and 0.49 +/- 0.17 microM (foetal liver, n.s.). V(max) for SULT1A1 (mean +/- SD) was 885 +/- 135 pmol min(-1) mg(-1) (adult liver) and 267 +/- 93 pmol min(-1) mg(-1) (foetal liver, p = 0.007). 4. The IC(50) of quercetin for SULT1A1 was measured in three samples of adult and foetal livers and was 13 +/- 2.1 and 12 +/- 1.4 nM, respectively. 5. The type of inhibition was mixed non-competitive in adult and foetal livers and K(i) was 4.7 +/- 2.5 nM (adult liver) and 4.8 +/- 1.6 nM (foetal liver). 6. In the adult liver, the intrinsic clearance (mean +/- SD) was 3.3 +/- 1.5 ml min(-1) mg(-1) (non-inhibited samples), 0.9 +/- 0.4 ml min(-1) mg(-1) (12.5 nM quercetin) and 0.5 +/- 0.06 ml min(-1) mg(-1) (25 nM quercetin). In the foetal liver, the intrinsic clearance (mean +/- SD) was 0.5 +/- 0.2 ml min(-1) mg(-1) (non-inhibited samples), 0.12 +/- 0.01 ml min(-1) mg(-1) (12.5 nM quercetin) and 0.2 +/- 0.09 ml min(-1) mg(-1) (25 nM quercetin). 7. In conclusion, quercetin is a potent inhibitor of human adult and foetal liver SULT1A1. It reduces the sulphation rate and intrinsic clearance of 4-nitrophenol in both human adult and foetal livers. This suggests that quercetin may inhibit the sulfation rate of those drugs sulphated by SULT1A1. The inhibition of SULT1A1 is complex and not due solely to competition at the catalytic site of SULT1A1.

Asunto(s)

Arilsulfotransferasa , Inhibidores Enzimáticos/farmacología , Hígado/enzimología , Quercetina/farmacología , Sulfotransferasas/antagonistas & inhibidores , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Feto/enzimología , Humanos , Técnicas In Vitro , Cinética , Masculino , Persona de Mediana Edad , Nitrofenoles/metabolismo , Fosfoadenosina Fosfosulfato/metabolismo , Sulfotransferasas/metabolismo

RESUMEN

The aim of this investigation was to study the methylation of quercetin and fisetin, 2 chemically related flavonoids, in human liver and to this purpose, an assay was set-up to measure the rates of quercetin and fisetin methylation in human liver. The methylation rates (pmol/min/mg) of quercetin and fisetin were measured in 10 liver samples and the mean +/- SD and the median were 170+/-30 and 177 (quercetin) and 183+/-15 and 178 (fisetin). The rates of quercetin and fisetin methylation were not different (p = 0.283). The fold of variation among samples was 2 (quercetin) and 1.3 (fisetin). Methyltransferase towards quercetin and fisetin followed Michaelis-Menten kinetics, and the Km values were 2.6+/-0.3 (quercetin) and 8.6+/-0.7 microM (fisetin, p = 0.009) and the Vmax values were 187+/-20 (quercetin) and 276+/-33 pmol/min/mg (fisetin, p = 0.009). Two, 4 and 8 microl of red Chianti wine added to the incubation mixture reduced the rate of quercetin methylation to 75+/-4%, 65+/-9% and 59+/-9%, respectively, and that of fisetin methylation to 62+/-3%, 51+/-3% and 44+/-4%, respectively. In conclusion, quercetin and fisetin are methylated in human liver and their rates of methylation have a limited variation among subjects.

Asunto(s)

Flavonoides/metabolismo , Quercetina/metabolismo , Adulto , Anciano , Femenino , Flavonoles , Frutas/química , Humanos , Técnicas In Vitro , Cinética , Hígado/metabolismo , Masculino , Metilación , Persona de Mediana Edad , Verduras/química , Vino

RESUMEN

OBJECTIVES: The first aim of this investigation was to study the variability of mycophenolic acid (MPA) glucuronidation rate in human liver. The second aim was to study the inhibition type of niflumic acid (NA) for MPA glucuronidation in human liver. The third aim was to study the variability of the IC(50) value of NA for MPA glucuronidation in human liver. METHODS: The rate of MPA glucuronidation was measured by employing an assay based on uridine 5'-diphosphate-[U-(14)C]-glucuronic acid (UDPGA), and MPA glucuronide was isolated by means of thin-layer chromatography. The necessary concentration for UDPGA and MPA was 1 mM. The rate of MPA glucuronidation was measured in 50 human liver samples. The inhibition type of NA for MPA glucuronidation was studied in 5 human liver samples. The NA IC(50) value was measured in 27 human liver samples using six concentrations of NA ranging from 1.05 microM to 34 microM. RESULTS: MPA glucuronidation rate was positively skewed, was not gender regulated and did not correlate with the liver donor's age. The rate of MPA glucuronidation varied 4.8-fold within the 5th and 95th percentiles, with a mean+/-SD and a median of 2.8+/-1.0 nmol/min/mg and 2.5 nmol/min/mg, respectively. The inhibition type of NA for MPA glucuronidation was mixed non-competitive. The Ki value of NA (mean+/-SD) was 15+/-10 microM and, in non-inhibited samples, the K(m) value for MPA was 0.41+/-0.06 mM. The distribution of NA IC(50) value varied 3.3-fold within the 5th and 95th percentiles with a mean+/-SD and a median of 5.6+/-2.1 microM and 5.2 microM, respectively. The distribution of NA IC(50) value did not deviate significantly from normality. CONCLUSION: The range of hepatic rate of MPA glucuronidation is narrow relative to those of ethinyloestradiol, testosterone and zidovudine glucuronidation obtained from literature. The Ki value of NA is one order of magnitude lower than the K(m) for MPA in non-inhibited samples. This indicates that the inhibitor affinity for glucuronosyl transferase is greater than that of the substrate. The range of variation of NA IC(50) values is narrow.

Asunto(s)

Antiinflamatorios no Esteroideos/farmacología , Glucuronosiltransferasa/metabolismo , Microsomas Hepáticos/efectos de los fármacos , Ácido Micofenólico/metabolismo , Ácido Niflúmico/farmacología , Adulto , Anciano , Interacciones Farmacológicas , Femenino , Humanos , Masculino , Microsomas Hepáticos/enzimología , Microsomas Hepáticos/metabolismo , Persona de Mediana Edad

RESUMEN

OBJECTIVE: The aim of the present study was to estimate the concordance rate between erythrocyte thiopurine methyltransferase (TPMT) activity and genotype at the TPMT locus in an Italian population sample. METHODS: The TPMT phenotype and genotype were determined in an unrelated population of 103 Italian healthy blood donors. Erythrocyte TPMT activity was measured with a radiochemical assay using 12.5 microM S-adenosyl-L-(methyl-14C)-methionine and 4 mM 6-mercaptopurine. The genotyping assay was based on restriction fragment length polymorphism polymerase chain reaction (RFLP-PCR) and allele-specific oligonucleotide polymerase chain reaction (ASO-PCR) methods. RESULTS: All subjects had detectable TPMT activity. The activity of TPMT varied 2.8-fold between the 5th and 95th percentile. This variation was neither age (P = 0.63) nor gender (P = 0.44) regulated and the frequency distribution of TPMT activity is compatible with a polymorphic distribution. The presence of the four most common defective alleles, i.e. TPMT*2, TPMT*3A, TPMT*3B and TPMT*3C, was examined through the entire phenotyped population. Ninety-two subjects did not carry any of the tested mutations. Eleven individuals were heterozygous for one of the mutant alleles and had a TPMT activity lower than 30 pmol/min/mg. Eight subjects were TPMT*1/TPMT*3A, two TPMT*1/TPMT*3C and one was TPMT*1/TPMT*2. The TPMT*3B allele was not detected in the samples analysed. CONCLUSION: There was a concordance of 97% between genotype and phenotype. All the heterozygotes had an intermediate phenotype. However, the wide variation range in TPMT activity detected in the wild-type homozygotes indicates that other genetic or epigenetic factors influence the TPMT phenotype.

Asunto(s)

Metiltransferasas/genética , Adulto , Femenino , Genotipo , Humanos , Italia , Masculino , Metiltransferasas/sangre , Persona de Mediana Edad , Fenotipo , Polimorfismo Genético/genética , Estadísticas no Paramétricas

RESUMEN

1. Quercetin is a natural flavonoid present in vegetables, fruit and wine, and is known to inhibit sulphotransferase. Drugs are often taken orally and the intestinal mucosa is an early site of drug metabolism. The aims of this investigation were to study the inhibition of dopamine, (-)-salbutamol, minoxidil and paracetamol sulphation by quercetin in the duodenal mucosa and liver and to compare the IC50 in these tissues. 2. The rates (pmol min(-1) mg(-1)) of sulphation of 4-nitrophenol were 343+/-92 (liver) and 164+/-22 (duodenum; p = 0.031), of dopamine were 15+/-11 (liver) and 656+/-516 (duodenum; p = 0.049), of (-)-salbutamol 153+/-31 (liver) and 654+/-277 (duodenum; p = 0.018), of minoxidil were 156+/-47 (liver) and 105+/-7 (duodenum; n.s.), and of paracetamol were 229+/-86 (liver) and 328+/-187 (duodenum; n.s.). 3. The IC50 of quercetin for 4-nitrophenol was 48+/-11 nM (liver) and 56+/-1 nM (duodenum, n.s.), for dopamine was 5.7+/-0.7 microM (liver) and 170+/-12 microM (duodenum, p < 0.0001), for (-)-salbutamol was 54+/-4 nM (liver) and 16+/-8 microM (duodenum; p = 0.025), for minoxidil was 134+/-22 nM (liver) and 3+/-0.3 microM (duodenum, p = 0.013), and for paracetamol was 57+/-7 nM (liver) and 35+/-1 microM (duodenum; p = 0.0002). 4. Quercetin inhibited the sulphation of 4-nitrophenol, dopamine, (-)-salbutamol, minoxidil and paracetamol both in liver and duodenum. With dopamine, (-)-salbutamol, minoxidil and paracetamol as substrates, quercetin was a more potent inhibitor in the liver than the duodenum. Such a difference may reflect the different composition of sulphotransferase forms in the liver and duodenum.

Asunto(s)

Duodeno/enzimología , Hígado/enzimología , Quercetina/farmacología , Sulfotransferasas/antagonistas & inhibidores , Acetaminofén/farmacología , Anciano , Albuterol/farmacología , Disponibilidad Biológica , Dopamina/farmacología , Interacciones Farmacológicas , Duodeno/efectos de los fármacos , Femenino , Frutas , Humanos , Concentración 50 Inhibidora , Hígado/efectos de los fármacos , Masculino , Persona de Mediana Edad , Minoxidil/farmacología , Quercetina/farmacocinética , Verduras , Vino

RESUMEN

OBJECTIVE: The aim of this investigation was to determine whether mefenamic acid and salicylic acid inhibit the sulfation of (-)-salbutamol and minoxidil in the human liver and duodenum, and if so, to ascertain whether the 50% inhibitory concentration (IC50) estimates are different in the two tissues. METHODS: Sulfotransferase activities were measured for 10 mM (-)-salbutamol and 5 mM minoxidil, and the concentration of 3'-phosphoadenosine-5'-phosphosulphate-[35S] was 0.4 microM. RESULTS: The IC50 estimates for (-)-salbutamol and minoxidil sulfation of mefenamic acid were 72 +/- 5.4 nM and 1.5 +/- 0.6 microM (liver), respectively, and 161 + 23 microM and 420 +/- 18 microM (duodenum), respectively. The figures for the liver were significantly lower (P < 0.0001) than those for the duodenum. The IC50 estimates for (-)-salbutamol sulfation of salicylic acid were 93 +/- 11 microM (liver) and 705 +/- 19 microM (duodenum, P < 0.0001). Salicylic acid was a poor inhibitor of minoxidil sulfation. CONCLUSION: The IC50 estimates for (-)-salbutamol sulfation of mefenamic acid and salicylic acid are lower than their unbound plasma concentrations after standard dosing, suggesting that mefenamic acid and salicylic acid should inhibit the hepatic sulfation of (-)-salbutamol in vivo.

Asunto(s)

Agonistas Adrenérgicos beta/farmacocinética , Albuterol/farmacocinética , Antiinflamatorios no Esteroideos/farmacología , Antihipertensivos/farmacocinética , Duodeno/metabolismo , Hígado/metabolismo , Ácido Mefenámico/farmacología , Minoxidil/farmacocinética , Anciano , Dopamina/metabolismo , Interacciones Farmacológicas , Duodeno/efectos de los fármacos , Femenino , Humanos , Hígado/efectos de los fármacos , Masculino , Persona de Mediana Edad , Nitrofenoles/metabolismo , Sulfatos/sangre

RESUMEN

1. Resveratrol, a polyphenolic compound present in grape and wine, has beneficial effects against cancer and protective effects on the cardiovascular system. Resveratrol is sulphated, and the hepatic and duodenal sulphation might limit the bioavailability of this compound. The aim of this study was to see whether natural flavonoids present in wine, fruits and vegetables inhibit the sulphation of resveratrol in the human liver and duodenum. 2. In the liver, IC50 for the inhibition of resveratrol sulphation was 12+/-2 pM (quercetin), 1.0+/-0.04 microM (fisetin), 1.4+/-0.1 microM (myricetin), 2.2+/-0.1 microM (kaempferol) and 2.8+/-0.2 microM (apigenin). Similarly, in the duodenum, IC50 was 15+/-2 pM (quercetin), 1.3+/-0.1 microM (apigenin), 1.3+/-0.5 microM (fisetin), 2.3+/-0.1 microM (kaempferol) and 2.5+/-0.3 microM (myricetin). 3. The type of inhibition of quercetin on resveratrol sulphation was studied in three liver samples and was determined to be non-competitive and mixed in nature. Km (mean+/-SD; microM) was 0.23+/-0.07 (control), 0.40+/-0.08 (5 pM quercetin) and 0.56+/-0.09 (10 pM quercetin). Vmax (mean+/-SD; pmol min(-1) x mg(-1)) was 99+/-11 (control), 73+/-15 (5 pM quercetin) and 57 +/- 10 (10 pM quercetin). Kj and Kies estimates (mean+/-SD) were 3.7+/-1.8 pM and 12.1+/-1.7 pM respectively (p = 0.010). 4. Chrysin was a substrate for the sulphotransferase(s) and an assay was developed for measuring the chrysin sulphation rate in human liver. The enzyme followed Michaelis-Menten kinetics and Km and Vmax (mean+/-SD) measured in four livers were 0.29+/-0.07 microM and 43.1+/-1.9 pmol x min(-1) x mg(-1) respectively. 5. Catechin was neither an inhibitor of resveratrol sulphation nor a substrate of sulphotransferase. 6. These results are consistent with the view that many, but not all, flavonoids inhibit the hepatic and duodenal sulphation of resveratrol, and such inhibition might improve the bioavailability of this compound.

Asunto(s)

Flavonoides/farmacología , Quempferoles , Quercetina/análogos & derivados , Estilbenos/antagonistas & inhibidores , Estilbenos/metabolismo , Sulfatos/metabolismo , Vino/análisis , Anciano , Apigenina , Disponibilidad Biológica , Duodeno/metabolismo , Femenino , Flavonoides/metabolismo , Flavonoles , Frutas/química , Humanos , Cinética , Hígado/metabolismo , Masculino , Persona de Mediana Edad , Quercetina/farmacología , Resveratrol , Especificidad por Sustrato , Sulfotransferasas/metabolismo , Verduras/química

RESUMEN

1. Resveratrol, a polyphenolic compound present in grapes and wine, has beneficial effects against cancer and protective effects on the cardiovascular system. It is present in the diet, and the hepatic and duodenal sulphation might limit the bioavailability of this compound. The aim was to study the sulphation of resveratrol in the human liver and duodenum. 2. A simple and reproducible radiometric assay for resveratrol sulphation was developed. It employed 3'-phosphoadenosine-5'-phosphosulphate-[35S] as the sulphate donor and the rates of resveratrol sulphation (mean +/- SD, pmol/min/mg cytosolic protein) were 90 +/- 21 (liver, n = 10) and 74 +/- 60 (duodenum, n = 10, p = 0.082). 3. Resveratrol sulphotransferase followed Michaelis-Menten kinetics and Km (mean +/- SD; microM) was 0.63 +/- 0.03 (liver, n = 5) and 0.50 +/- 0.26 (duodenum, n = 5, p = 0.39) and Vmax (mean +/- SD, pmol/min/mg cytosolic protein) were 125 +/- 31 (liver, n = 5) and 129 +/- 85 (duodenum, n = 5, p = 0.62). 4. Resveratrol sulphation was inhibited by the flavonoid quercetin, by mefenamic acid and salicylic acid, two commonly used non-steroidal anti-inflammatory drugs. IC50 of resveratrol sulphation for quercetin was 12 +/- 2 pM (liver) and 15 +/- 2 pM (duodenum), those for mefenamic acid were 24 +/- 3 nM (liver) and 11 +/- 0.6 nM (duodenum), and those for salicylic acid were 53 +/- 9 microM (liver) and 66 +/- 4 microM (duodenum). 5. The potent inhibition of resveratrol sulphation by quercetin, a flavonoid present in wine, fruits and vegetables, suggests that compounds present in the diet may inhibit the sulphation of resveratrol, thus improving its bioavailability.

Asunto(s)

Duodeno/metabolismo , Hígado/metabolismo , Rosales/química , Estilbenos/metabolismo , Sulfatos/metabolismo , Vino , Adulto , Anciano , Disponibilidad Biológica , Duodeno/efectos de los fármacos , Duodeno/enzimología , Humanos , Cinética , Hígado/efectos de los fármacos , Hígado/enzimología , Ácido Mefenámico/farmacología , Persona de Mediana Edad , Estructura Molecular , Fosfoadenosina Fosfosulfato/metabolismo , Quercetina/farmacología , Resveratrol , Ácido Salicílico/farmacología , Estilbenos/farmacocinética , Estilbenos/farmacología , Sulfotransferasas/antagonistas & inhibidores , Sulfotransferasas/metabolismo

RESUMEN

OBJECTIVE: The aim of this investigation was to study the inhibition of 11 nonsteroidal anti-inflammatory drugs (NSAIDs) on the human liver phenol sulfotransferases (HL-PST) and catechol sulfotransferase (HL-CST). METHODS: The activities of HL-PST and HL-CST were measured with 4 microM 4-nitrophenol and 60 microM dopamine (the sulfate acceptors) and 0.4 microM 3'-phosphoadenosine-5'-phosphosulfate [35S] (the sulfate donor). Samples of liver were obtained from five patients, aged 55-79 years, undergoing clinically indicated hepatectomy. The inhibition curves were constructed with at least five concentrations of the inhibitor. RESULTS: With the exception of piroxicam, NSAIDs inhibited HL-PST, and the estimates of the inhibitory concentration for 50% of responses (IC50; microM) were: 0.02 (mefenamic acid), 3.7 (diflunisal), 5.4 (nimesulide), 9.5 (diclofenac), 30 (salicylic acid), 41 (ketoprofen), 74 (indomethacin), 159 (ibuprofen), 245 (ketoralac) and 473 (naproxen). With 4-nitrophenol as the variable substrate, the inhibition of salicylic acid on HL-PST was non-competitive and the Ki and Kies were 18 microM and 21 microM (n = 5; P = 0.548), respectively. HL-CST was less susceptible than HL-PST to inhibition by NSAIDs, with only five drugs inhibiting this enzyme. The IC50 estimates for these drugs (microM) were 76 (mefenamic acid), 79 (diflunisal), 103 (indomethacin), 609 (salicylic acid) and 753 (diclofenac). CONCLUSION: The comparison of the IC50 estimates of HL-PST with the therapeutic plasma concentrations of NSAIDs corrected for the plasma unbound fraction was consistent with the view that mefenamic acid and salicylic acid, when administered at therapeutic doses, should impair the hepatic sulfation of those compounds that are substrates of phenol sulfotransferase.

Asunto(s)

Antiinfecciosos/farmacología , Antiinflamatorios no Esteroideos/farmacología , Arilsulfotransferasa/antagonistas & inhibidores , Hígado/metabolismo , Ácido Salicílico/farmacología , Anciano , Arilsulfotransferasa/metabolismo , Femenino , Humanos , Hígado/efectos de los fármacos , Masculino , Persona de Mediana Edad

RESUMEN

1. The inhibition of the human liver phenol sulphotransferase (HL-PST) and catechol sulphotransferase (HL-CST) by five fenamates has been studied and the activities of HL-PST and HL-CST were measured with 4-nitrophenol and dopamine as substrates, respectively. 2. The IC50 for inhibition of HL-PST were 0.02 microM (mefenamic acid); 0.12 microM (tolfenamic acid); 0.28 microM (niflumic acid); 0.87 microM (meclofenamic acid) and 1.50 microM (flufenamic acid). 3. HL-CST was less susceptible than HL-PST to the inhibition by fenamates and the IC50 for HL-CST were 36 microM (tolfenamic acid); 70 microM (flufenamic acid); 76 microM (mefenamic acid); 180 microM (niflumic acid) and 185 microM (meclofenamic acid). 4. The ratios of the IC50 for HL-CST:HL-PST were drug-dependent and ranged from 47 (flufenamic acid) to 3800 (mefenamic acid). Mefenamic acid is a relatively potent and selective inhibitor of HL-PST. 5. The IC50 for HL-PST obtained with mefenamic acid was three orders of magnitude lower than the peak plasma concentration of this drug after an oral dose of 0.5 g. Accordingly, mefenamic acid should impair sulphation in vivo.

Asunto(s)

Arilsulfotransferasa/antagonistas & inhibidores , Inhibidores Enzimáticos/farmacología , Hígado/enzimología , ortoaminobenzoatos/farmacología , Dopamina/metabolismo , Ácido Flufenámico/farmacología , Humanos , Hígado/efectos de los fármacos , Ácido Meclofenámico , Ácido Mefenámico/sangre , Ácido Mefenámico/farmacología , Estructura Molecular , Nitrofenoles/metabolismo

RESUMEN

1. Resveratrol, a polyphenolic compound present in grape and wine, has beneficial effects against cancer and protective effects on the cardiovascular system. It has been shown that the compound is sulphated in human liver and the aims of the present investigation were to study resveratrol glucuronidation in human liver microsomes and to determine whether flavonoids inhibit resveratrol glucuronidation. 2. A simple and reproducible radiometric assay for resveratrol glucuronidation was developed. The assay employed uridine-5'-diphosphoglucuronic acid-[14C] and unlabelled resveratrol. Resveratrol-glucuronide was isolated by TLC. The intra- and interassays variabilities were 1 and 1.5%, respectively. 3. The rate of resveratrol glucuronidation was measured in 10 liver samples. The mean +/- SD and median of resveratrol glucuronidation rate were 0.69 +/- 0.34 and 0.80 nmol/min/mg, respectively. Resveratrol glucuronosyl transferase followed Michaelis-Menten kinetics and the Km and Vmax (mean +/- SD; n = 5) were 0.15 +/- 0.09 mM and 1.3 +/- 0.3 nmol/min/mg, respectively. The intrinsic clearance was 11 +/- 4 x 10(-3) ml/min.mg. 4. The flavonoid quercetin inhibited resveratrol glucuronidation and its IC50 (mean +/- SD; n = 3) was 10 +/- 1 microM. Myricetin, catechin, kaempferol, fisetin and apigenin (all at 20 microM) inhibited resveratrol glucuronidation and the percent of control ranged between 46% (catechin) to 72% (apigenin). 5. The present results show that resveratrol is glucuronated in the human liver. Glucuronidation may reduce the bioavailability of this compound however, flavonoids inhibit resveratrol glucuronidation and such an inhibition might improve the bioavailability of resveratrol.

Asunto(s)

Inhibidores Enzimáticos/metabolismo , Inhibidores Enzimáticos/farmacocinética , Ácido Glucurónico/metabolismo , Quempferoles , Hígado/efectos de los fármacos , Hígado/metabolismo , Quercetina/análogos & derivados , Rosales/metabolismo , Estilbenos/metabolismo , Estilbenos/farmacocinética , Vino , Adulto , Anciano , Apigenina , Catequina/farmacología , Cromatografía en Capa Delgada , Relación Dosis-Respuesta a Droga , Femenino , Flavonoides/farmacología , Flavonoles , Humanos , Concentración de Iones de Hidrógeno , Concentración 50 Inhibidora , Cinética , Masculino , Microsomas Hepáticos/metabolismo , Persona de Mediana Edad , Quercetina/farmacología , Reproducibilidad de los Resultados , Resveratrol

RESUMEN

The endogenous concentration of uridine 5'-diphosphoglucoronic acid (UDPGLcUA), the endogenus substrate of UDP-glucuronosyltransferase, was measured in the human fetal and adult liver and kidney and in the placenta. The concentrations (mumol/Kg wet weight) of UDPGLcUA were 59.4 +/- 11.3 (fetal liver), 301 +/- 119 (adult liver), 11.9 +/- 3.2 (fetal kidney), 17.4 +/- 3.0 (adult kidney), 17.8 +/- 1.8 (mid-term placenta) and 17.0 +/- 1.7 (term placenta). UDPGLcUA is present in the human fetal liver at a concentration 5-fold lower than in the adult liver indicating a potential limiting factor for glucuronidation ind the human fetus.

Asunto(s)

Feto/química , Riñón/química , Hígado/química , Placenta/química , Uridina Difosfato Ácido Glucurónico/análisis , Adulto , Anciano , Femenino , Glucuronosiltransferasa/metabolismo , Humanos , Masculino , Persona de Mediana Edad , Embarazo