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  • 1
    ISSN: 1432-0738
    Keywords: Key wordsCYP2A6 polymorphism ; Coumarin ; Nicotine ; Japanese ; Caucasian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Genotypes of CYP2A6, namely CYP2A6 * 1 (wild-type), CYP2A6 * 2, and CYP2A6 * 3, were examined in liver DNA of 39 Japanese and 43 Caucasians using two-step polymerase chain reaction (PCR) methods. We first amplified a DNA fragment (1725 bp) located between near middle of exon 1 and end of exon 4 of the CYP2A6 gene and further amplified using a forward primer 't' or 'mut' (middle of exon 3) and a reverse primer 'E3R' (middle of intron 3) for the detection of CYP2A6 * 2-genetic polymorphism. The 1725 bp fragment was also used for the amplification between exon 3 and near middle of intron 3 of the CYP2A6 gene and the fragment thus obtained digested with XcmI or DdeI to detect and confirm the CYP2A6 * 2- and CYP2A6 * 3-types, respectively. Only one DNA sample from a Japanese origin (J18) was not amplified by CYP2A6-specific primers; liver microsomes from this individual had very low activity of coumarin 7-hydroxylation and were devoid of protein(s) immunoreactive to anti-CYP2A6 antibody. Thus, this individual was suggested to be due to the gene deletion in CYP2A6. By analyzing the remaining 38 Japanese and 43 Caucasians, we found that there were no cases of CYP2A6 * 3-type polymorphism in the samples examined in this study, and no cases of CYP2A6 * 2-type polymorphism in the Japanese samples. Of Caucasians studied two individuals were classified into heterozygous CYP2A6 * 1/ * 2-type. Liver microsomal coumarin 7-hydroxylation activities in these two Caucasians were found to be lower than those of the other 41 Caucasians. Kinetic analysis showed that two CYP2A6 * 1/ * 2 individuals had a very low ratio of V max to K m for nicotine C-oxidation as well as coumarin 7-hydroxylation in liver microsomes, compared with those of homozygous CYP2A6 * 1-type. These results suggest that among 39 Japanese and 43 Caucasians examined one Japanese is classified to be CYP2A6 gene deletion and two Caucasians are heterozygous CYP2A6 * 1/ * 2-genotype. Thus the race-related differences in the occurrence of CYP2A6 genetic polymorphisms were supported.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: P-glycoprotein ; 1,4-dihydropyridine calcium antagonists ; inhibition ; cytochrome P450 3A4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Recently, we clarified the inhibitory effects of 13 kinds of 1,4-dihydropyridine calcium antagonists on human cytochrome P450 (CYP) 3A4. It has been reported that the substrates and/or inhibitors are overlapped between CYP3A4 and P-glycoprotein (P-gp). The purpose of this study was to investigate the inhibitory effects of 13 kinds of 1,4-dihydropyridine calcium antagonists on P-gp-mediated transport in order to evaluate the overlapping specificity of the inhibitors between P-gp and CYP3A4. Methods. The transcellular transports of [3H]daunorubicin or [3H]digoxin by monolayers of LLC-GA5-COL150 cells in which P-gp was overexpressed were measured in the presence or absence of the 1,4-dihydropyridine calcium antagonists. Results. The transport of [3H]daunorubicin was strongly inhibited by manidipine, barnidipine, benidipine, (−)-efonidipine, nicardipine, (+)-efonidipine, and amlodipine with the IC50 values of 4.6, 8.6, 9.5, 17.3, 17.5, 20.6, and 22.0 μM, respectively. The transport of [3H]digoxin was strongly inhibited by benidipine, nicardipine, barnidipine, and manidipine. Conclusions. It was clarified that 13 kinds of 1,4-dihydropyridine calcium antagonists have different inhibitory potencies and substrate specificities to the transport of [3H]daunorubicin or [3H]digoxin. Some compounds did not demonstrate the overlapping specificity for inhibition between P-gp and CYP3A4. It was also clarified that ni- cardipine, benidipine, manidipine, and barnidipine were strong inhibitors of P-gp as well as CYP3A4.
    Type of Medium: Electronic Resource
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