Effects of aspirin on arylamineN-acetyltransferase activity and DNA adducts in human bladder tumour cells
7
Citation
26
Reference
10
Related Paper
Citation Trend
Abstract:
Aspirin (acetylsalicylic acid) was used to determine the inhibition of arylamine N-acetyltransferase (NAT) activity and DNA adduct formation in a human bladder tumour cell line (T24). The activity of NAT was measured by high-performance liquid chromatography, assaying for the amounts of N-acetyl-2-aminofluorene and N-acetyl-p-aminobenzoic acid and remaining 2-aminofluorene and p-aminobenzoic acid. Two assay systems were used: one with cytosol and the other with intact cells. High-performance liquid chromatography was also used to analyse for the 2-aminofluorene-DNA adducts. Intact bladder tumour cells were used. The results demonstrated that NAT activity and 2-aminofluorene-DNA adduct formation in human bladder tumour cells were inhibited by acetylsalicylic acid in a dose-dependent manner. The effects of acetylsalicylic acid on the values of the apparent K(m) and V(max) were also determined in both examined systems. The data also indicated that acetylsalicylic acid decreased the apparent values of K(m) and V(max) from human bladder tumour cells in both cytosol and intact cells.Keywords:
Nat
Arylamine N-acetyltransferase
N-acetyltransferase
Nat
Arylamine N-acetyltransferase
N-acetyltransferase
Acetyltransferases
Cite
Citations (0)
Arylamine N-acetyltransferase (NAT) activity was identified and partially characterized in the bovine lens. According to size-exclusion HPLC, the molecular mass of the arylamine NAT is approximately 30-kDa. Based upon substrate specificity analysis, it is best described as an arylamine NAT which has some ability to N-acetylate arylalkylamines. This arylamine NAT acetylates para-aminobenzoic acid thereby demonstrating a monomorphic pattern of N-acetylation. It demonstrates low sensitivity to methotrexate inhibition as indicated by the relatively high IC50 value (470 microM). NAT could be involved in lenticular detoxification of both endogenous amines and exogenous drugs.
Nat
Arylamine N-acetyltransferase
N-acetyltransferase
IC50
Cite
Citations (4)
Arylamine N-acetyltransferase (NAT) is an important phase II metabolizing enzyme that influences drug efficacy and adverse effects. Here, we report a long-lived luminescent lanthanide complex as a probe for NAT, employing an intraligand photoinduced electron transfer strategy. The probe shows approximately 100-fold increase of luminescence upon N-acetylation catalyzed by NAT, with relatively high specificity for NAT2 over NAT1. It is the first NAT probe that is suitable for sensitive, homogeneous, and rapid detection of NAT activity of recombinant enzyme or cell lysate, and is expected to be useful for drug discovery and clinical diagnosis.
Nat
Arylamine N-acetyltransferase
N-acetyltransferase
Cite
Citations (44)
The effects of p-aminobenzoic acid (PABA), procainamide (PA), anisidine (AN) and isoniazid (INH) on N-acetyltransferase (NAT) activities in cultured human cells were determined. PABA increased the specific activity of PABA NAT in the U937 cells but not in the Hep G2 cells. The enzyme activity in the PABA-treated U937 cells was restored to normal within 4 d after removing PABA from medium. These results imply that the PABA NAT activity in the U937 cells can be induced by PABA and the PABA NAT in the U937 cells is different from that in the Hep G2 cells. INH increased the INH NAT specific activity in the U937 cells but decreased the PABA NAT activity. AN decreased both the AN NAT and the PABA NAT specific activities in the U937 cells. PA did not affect the specific activities of PABA NAT or glucose-6-phosphate dihydrogenase (G-6-P DH) in the U937 cells. PABA also increased the specific activities of AN NAT and G-6-P DH. This implies that the induction effect of PABA on the PABA NAT activity is not specific. In this study the PABA NAT specific activity was increased only by PABA, and the INH NAT activity only by INH. However, the AN NAT activity could be induced by PABA but not by AN. These results indicate that induction of some but not all NAT activities has a limiting specificity.
Nat
U937 cell
Arylamine N-acetyltransferase
N-acetyltransferase
Cite
Citations (0)
Abstract This unit describes methods for measuring the activity of arylamine N‐acetyltransferases (NAT). Genetic polymorphisms in NAT 1 and NAT 2 have been associated with susceptibility to aromatic amines carcinogens and effects of therapeutic drugs. Evaluation of the activities associated with substrates of NATs is helpful in elucidating the contribution of these enzymes to the pharmacologic and toxicologic effects of arylamines and hydrazines.
Nat
Arylamine N-acetyltransferase
Acetyltransferases
N-acetyltransferase
Acetyltransferases
Cite
Citations (2)
N-Acetylation plays an important role in the metabolism of a wide variety of hydrazine drugs and arylamine drugs and carcinogens. Humans have genetically determined differences in their N-acetyltransferase activities and are phenotypically classified as rapid or slow acetylators. Mice have a similar genetic polymorphism in N-acetyltransferase activity and have been used as models of the human polymorphism in many studies of the toxicology and carcinogenicity of arylamines. Recently, two N-acetyltransferase genes, Nat-1 and Nat-2, were cloned from rapid (C57BL/6J) and slow (A/J) acetylator mouse strains. The genomic clone encoding NAT-1 is identical in rapid and slow acetylator mouse strains, whereas the clone encoding NAT-2 differs between rapid and slow strains by a single base pair, which changes the encoded amino acid from Asn99 in the rapid acetylator strain to Ile99 in the slow acetylator strain. In this report, the N-acetylation polymorphism in mice was investigated by transiently expressing the cloned N-acetyltransferase genes in COS-1 cells. The intronless coding regions of Nat-1 and Nat-2 showed different substrate specificities; isoniazid was a preferred substrate for NAT-1, whereas p-aminobenzoic acid was preferred for NAT-2(99asn) and NAT-2(99ile). All three enzymes acetylated 2-aminofluorene, but none of them acetylated sulfamethazine. Kinetic constants determined for the expressed enzymes with 2-aminofluorene and p-aminobenzoic acid indicated that Km values were not significantly different between the enzymes, although the Vmax value of NAT-2(99asn) was consistently 2-3-fold higher than that of NAT-1 or NAT-2(99ile). Nat-1 and Nat-2 encoded mRNAs of approximately 1.4 kilobases in livers of rapid and slow acetylators. Nat-2 mRNA was more abundant in liver than Nat-1 mRNA. The abundance of Nat-2 mRNA and Nat-1 mRNA was equivalent in both rapid and slow acetylator mouse strain livers. Incubation of transfected COS-1 cell cytosols at 37 degrees showed that the time for decline of NAT activity to 50% of its initial value was 45 hr for NAT-1, 60 hr for NAT-2(99asn), and 4 hr for NAT-2(99ile). This 15-fold difference in the heat stability of the rapid and slow isoforms of NAT activity was also observed in cytosols from rapid and slow acetylator livers. Comparison of the rates of translation of the rapid and slow isoforms of NAT-2 in an in vitro system showed that NAT-2(99asn) was translated at approximately twice the rate of NAT-2(99ile).(ABSTRACT TRUNCATED AT 400 WORDS)
Nat
N-acetyltransferase
Acetyltransferases
Acetyltransferases
Arylamine N-acetyltransferase
Cite
Citations (51)
Arylamine N-acetyltransferase (NAT) activity was partially purified and characterized in bovine retina. Upon examining the retinal supernatant for multiple ionic species, only one NAT activity was detected. Based upon its substrate specificity, it is best described as an arylamine NAT. According to size-exclusion HPLC, the molecular mass of the arylamine NAT is approximately 30-kDa. This arylamine NAT acetylates p-aminobenzoic acid thereby demonstrating a monomorphic pattern of acetylation. The NAT activity demonstrated low sensitivity to methotrexate inhibition as indicated by a high IC50 value (480 microM).
Nat
Arylamine N-acetyltransferase
IC50
N-acetyltransferase
Acetyltransferases
Cite
Citations (7)
Nat
N-acetyltransferase
Arylamine N-acetyltransferase
Acetyltransferases
Cite
Citations (32)
The inhibition of arylamine N -acetyltransferase (NAT) activity by ibuprofen was determined in a human colon tumour (adenocarcinoma) cell line. Two assay systems were employed, one with cellular cytosols (9000 g supernatant) and the other with intact colon tumour cell suspensions. The NAT activity in a human colon tumour cell line was inhibited by ibuprofen in a dose-dependent manner in both systems, i.e. the greater the concentration of ibuprofen in the reaction, the greater the inhibition of NAT activities in both systems. The data also indicated that ibuprofen decreases the apparent Km and Vmax of NAT enzyme from human colon tumour cells in both systems examined. This report is the first demonstration to show that ibuprofen affects human colon tumour cell NAT activity. © 1998 John Wiley & Sons, Ltd.
Nat
Ibuprofen
Arylamine N-acetyltransferase
N-acetyltransferase
Cite
Citations (6)
Regional distribution of arylamine and arylalkylamineN-acetyltransferase activities in the rat brain
Arylamine and arylalkylamine N-acetyltransferase (NAT) activities were measured separately in different areas of the rat brain using specific substrates. Relatively high levels of arylamine NAT activity were detected in all areas examined. Arylalkylamine NAT activity in these areas ranged from 2 to 5% of the arylamine NAT activity. The possibility that arylamine NAT may be involved in the control of kynurenine metabolism in the brain is discussed.
Nat
Arylamine N-acetyltransferase
N-acetyltransferase
Cite
Citations (21)