ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Experiments were performed invivoand invitroto 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 6ß 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.

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Fourteen drug free healthy volunteers and 22 psychiatric patients under psychotropic medication were phenotyped for their individual CYP2D6 activity using dextromethorphan as a probe drug. A solution containing 20 mg dextromethorphan was administered and blood was taken 60 in in later for determination of dextromethorphan and metabolites in serum. For comparison, urine was collected over 8 h after ingestion of 20 mg dextromethorphan in a separate test. The CYP2D6 phenotype was determined from the ratio of dextromethorphan to dextrorphan. For genotyping, mutant alleles of the CYP2D6 gene were identified using allele-specific polymerase chain reactions. Genotyping revealed five poor metabolizers of CYP2D6. The others were extensive metabolizers. The ratio of dextromethorphan to dextrorphan ranged from 0.01-2.53 in serum and from 0.0007-4.252 in urine. Probit analysis of serum ratios revealed a bimodal distribution with an antimode at 0.126. According to this antimode, control subjects exhibited identical phenotypes and genotypes, whereas patients under paroxetine, moclobemide or metoprolol who had been genotyped as extensive metabolizers were poor metabolizer phenotypes. Administration of tricyclic antidepressants did not change the CYP2D6 phenotype. The serum assay was more rapid and more accurate than the standard urine approach. Therefore the determination of dextromethorphan and metabolites in serum could be advantageous to measure individual CYP2D6 activities in vivo and thus optimize the dosing of drugs metabolized by CYP2D6.

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Previous studies of associations of metabolic polymorphisms with the occurrence of malignant brain tumors have suggested that there is a significantly increased risk of development of adult gliomas in individuals who carry a poor metabolizer CYP2D6 variant allele and the GSTTI null genotype. To investigate this further, a population-based case control study of adult glioma in the San Francisco Bay area was conducted. Patients (n=188) diagnosed with brain tumors and controls (n=166) were enrolled using random digit dialing and were frequency matched for age, ethnicity and gender. Genotyping for the polymorphisms was performed using standard PCRbased techniques. The analysis of the data was restricted to Caucasians because the prevalence of these traits is known to vary by ethnicity. No overall association of either the GSTTI null genotype or CYP2D6 homozygous variant PM genotype was observed with the occurrence of brain tumors. However, when stratified by histopathologic subtype, there was a significantly increased risk for oligodendroglioma associated with the GSTTI null genotype, with an OR of 3.2 (95% CI 1.1-9.2). These data suggest that the GSTTI polymorphism may play a role in the development of a subset of malignant brain tumors in adults, and indicate the need for further studies.

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Human cytochrome F450 2D6 metabolizes more than 50 common drugs and is polymorphically expressed, with 5-10% of the population lacking expression caused by mutant genes. This may result in a defective and toxic response in deficient individuals treated with 2D6 drug substrates. Baculovirus-expressed 2D6 was used to immunize mice for hybridoma production and two clones yielded monoclonal antibodies, that were positive against 2D6 by ELISA and inhibited 2D6 catalysed metabolism of bufuralol, dextromethorphan and phenanthrene by more than 90%. The inhibitory activity was highly specific to 2D6 and the monoclonal antibodies did not bind to 11 other P450s, nor inhibit seven human P450s tested. Analysis of eight human liver microsome samples showed that their basal bufuralol I'-hydroxylase activity varied from 6.7-83.5 pmol min-1nmol-1P450. The monoclonal antibody 512-1-8 inhibited 2D6-dependent bufuralol I'-hydroxylase in these samples by 10-70% indicating a widely variable role for 2D6 in human liver bufuralol I'-hydroxylase activity and a role for other P450s in bufuralol metabolism. Independent analysis of several recombinant human P450s showed that 2D6, 2C8, 2C9, 2C19 and 1A2 exhibited bufuralol I'-hydroxylase activity with 2D6 and 2C19 being the most active. Further analysis of three liver samples was made with individual inhibitory monoclonal antibodies. Inhibitory antibodies to 2D6, 2B6, 2111, 2C8/9/19, 3A4 and 1A2 were added to the microsomes either singly or additively. Inhibitory activity of bufuralol I'-hydroxylase was observed with antibodies to 2D6 (14-76%), 2C8/9/19 (24-69%) and 1A2 (2-25%) indicating a variable and different role for each of these P450s in the bufuralol I'-hydroxylase of human liver. The monoclonal antibodies to 2B6, 2E1 and 3A4 were not inhibitory, indicating that these enzymes play no role in bufuralol I'-hydroxylase metabolism. When the three antibodies to 2D6, 2C8/9/19 and 1A2, respectively, were all added, the total bufuralol I'-hydroxylase of the liver samples was inhibited by more than 90%, indicating that the latter P450s catalyse all of liver bufuralol I'-hydroxylase metabolism. These studies demonstrate that inhibitory monoclonal antibodies offer a simple and precise method for assessing the quantitative role of each P450 in the metabolism of a P450 substrate in a tissue, which include drugs, carcinogens, mutagens, toxic chemicals and endobiotics.

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The relationship between a dopamine D2 receptor genetic polymorphism at the TaqA A locus and the level of D2 receptor binding was investigated in normal, middle aged to elderly subjects with no psychiatric or neurological disorders. D2 receptor binding was measured by autoradiography in the caudate, putamen and nucleus accumbens, using the specific D2 receptor ligand [3H]-raclopride. In a sample of 44 individuals, only one was homozygous for the A1 allele, 2 5 were homozygous for A2 and 18 were heterozygotes. The presence of one or two A1 alleles was associated with reduced D2 receptor binding in all areas of the striatum, reaching statistical significance in the ventral caudate and putamen (p=0.01 and p=0.044, respectively). This reduction was more marked in males than females, particularly in the putamen. A genetic predisposition to lower D2 receptor expression may increase susceptibility to neuroleptic medication or clinical symptoms that are associated with diseases involving dopaminergic pathology.

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Two missense mutations were uncovered in the IIGT1A6 (HLUG PI) cDNA which codes for a human phenol-metabolizing UDP-glucuronosyltransferase. The mutant and a wild- type IJGT1A6 cDNAs were isolated from a custom synthesized human liver λ Zap cDNA library. Both an A to G transition at nucleotide 541 (T181 A) and an A to C transversion at nucleotide 552 (R184S) occurred in exon 1 of the UGT1A6 (UGT1F) gene at the UGT1 locus. The two mutations on a single allele created a heterozygous genotype. Newly created Bsml and BsoFl sites at the T181 A and Rl 84S locations, respectively, were confirmed by endonuclease treatment of PCR-generated DNA using the donor-liver genomic DNA as template. Screens with endonuclease treatment showed that 33/98 DNA samples were heterozygous with both mutations on one allele. One other individual also carried the Rl 84S mutation on the second allele. Wild-type UGT1A6 generated a broad plateau of activity from pH 5.0 to pH 8.0 with certain experimental phenols, while activity was 1.3-2.5-fold higher at pH 6.4 than at pH 7.2 for others. UGT1A*2 (181 A+ and 184S+) metabolized 4-nitrophenol, 4-tert-butylphenol, 3-ethylphenoI/4-ethylphenol, 4-hydroxycoumarin, butylated hydroxy anisole and butylated hydroxy toluene, with the pH 6.4 preference, at only 27-75% of the rate of the wild-type isozyme whereas 1-naphthol, 3-iodophenol, 7-hydroxycoumarin, and 7-hydroxy-4-methylcoumarin were metabolized at essentially the normal level. Furthermore, UGT1 A6*2 metabolized 3-O-methyl-dopa and methyl salicylate at 41-74% of that of the wild-type, and a series of P-blockers at 28-69% of the normal level. This evidence suggests that the UGT1A6 enzyme activity is affected by different amino acids depending upon the substrate selection.

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

A study of the metabolism of trimethylamine was carried out in 103 healthy Thai volunteers (70 men and 33 women) and it was found that under normal dietary conditions 84—100% of trimethylamine was excreted in the urine in its JV-oxide form. Five propositi living in different parts of the country were identified as having deficiency in the JV-oxidation of this tertiary amine, because they excreted only 8-35% of this chemical as trimethylamine N-oxide. This metabolic defect was also confirmed by the results of an oral trimethylamine (600 mg) challenge experiment in which all five propositi were found to excrete an even smaller percentage of trimethylamine as trimethylamine N-oxide in their urine. The results of a study of the families of the two proband individuals, as well as those members of their preceding generations under normal dietary conditions, are consistent with the view that the disorder or metabolic defect is inherited in a Mendclian fashion as an autosomal recessive trait, similar to that reported for white Caucasian subjects.

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Data on both the incidence of slow acetylator phenotype of probe drugs isonia/id, sulfadimidine or sulfametha/ine, caffeine and dapsone in mainland or overseas Chinese, and the distribution of NAT2 genotypes and the frequency of NAT2 alleles in the Chinese populations were summarized and reanalysed using a meta-analysis method. Frequency of the slow acetylator phenotype in 3516 healthy Han Chinese gave an overall mean of approximately 19.9 ± 4.0%, with the range of the combined data being between 1 5.8% and 25.5%. In addition, frequencies of the slow acetylator phenotype differ between the different minorities in Chinese populations and the range was between 3.2% and 50.6%, with a mean value of 20.6 ± 12.9% in a total of 1842 individuals from 17 Chinese minorities. In addition, there was no significant heterogeneity in overseas Chinese between the probe drugs isoniazid and sulfadimidine or sulfamethazine (χ=5.97, df=4; p>0.05), and the mean value of slow acetylator phenotype incidence was 24.5% (119/485; 95%CI: 20.7-28.3%), consistent with that of the native Chinese. As expected, frequency of the slow acetylator genotypes in Chinese populations was 25.4% (1 12/441; 95%CI: 21.3-29.5%), which was in accordance with that of the slow acetylator phenotype in native or overseas Chinese. For all genotypes, *4/*4 (29.9%, 132/441), *4/*6/A (27.4%, 121/441), *4/7A (12%, 53/441) and *6A/*6A (11.3%, 50/441) occupied 80.6%, but *5A/*7/A (0.2%, 1/441), *5A/*5A (1.1%, 5/441) and 97A/*7A (1.8%, 8/441) were not frequently found. From this report, the genotype frequencies of homozygous rapid acetylator, heterozygous rapid acetylator, and homozygous slow acetylator were found to be 0.299 (1 32/441), 0.447 (197/441) and (K254 (112/441), respectively. Furthermore, both *4 (52.3%; 95%CI: 49-56%) and 6A (30.5%; 95%CI: 28-34%) were major NAT2 alleles, while *7A (11.2%; 95%CI: 9-1 3%) and *54 (6%; 95%CI: 4-8%) were uncommonly present. Frequency of the mutant alleles was observed at 0.477 (421 /882 alleles). The *7A constituted 23.5% 1(99/421) of slow acetylator alleles in Chinese populations, showing that this point mutation exists not only in Oriental or Asiatic, but also in Chinese populations. According to the Hardy-Weinberg equilibrium, in the phenotyped Chinese populations, the mean estimate of predicted allelic frequencies of the genotypes RR, Rr, and rr was 0.294, 0.496, and 0.210 for the Chinese, and the expected frequency of the deficient gene r was 0.458. By comparison, the predicted values are in complete agreement with the observed ones. In conclusion, this meta-analysis determined the accurate population frequencies of phenotype and genotype of the NAT2 genetic deficiency in healthy Chinese subjects.

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID

ISSN:0960-314X    

出版商:OVID    

年代:1997

数据来源: OVID