Received for publication February 26, 2007.
Revised March 29, 2007.
Accepted for publication March 29, 2007.

Effect of arylamine acetyltransferase Nat3 gene knockout on N-acetylation in the mouse

Abstract

Arylamine N-acetyltransferases (NATs) catalyze the biotransformation of many important arylamine drugs and procarcinogens. NATs can either detoxify or activate procarcinogens, complicating the manner in which these enzymes may participate in enhancing or preventing toxic responses to particular agents. Mice possess three NAT isoenzymes, Nat1, Nat2 and Nat3. While Nat1 and Nat2 can efficiently acetylate many arylamines, few substrates appear to be appreciably metabolized by Nat3. We generated a Nat3 knockout mouse strain and used it along with our double Nat1/2(-/-) knockout strain to further investigate the functional role of Nat3. Nat3(-/-) mice showed normal viability and reproductive capacity. Nat3 expression was very low in wild-type animals and completely undetectable in Nat3(-/-) mice. In contrast, greatly elevated expression of Nat3 transcript was observed in Nat1/2(-/-) mice. We used a transcribed marker polymorphism approach to establish that the increased expression of Nat3 in Nat1/2(-/-) mice is a positional artifact of insertion of the PGK-neomycin resistance cassette in place of the Nat1/Nat2 gene region and upstream of the intact Nat3 gene, rather than a biological compensatory mechanism. Despite the increase in Nat3 transcript, the N-acetylation of p-aminosalicylate, sulfamethazine, 2-aminofluorene and 4-aminobiphenyl was undetectable either in vivo or in vitro in Nat1/2(-/-) animals. In parallel, no difference was observed in the in vivo clearance or in vitro metabolism of any of these substrates between wild-type and Nat3(-/-) mice. Thus Nat3 is unlikely to play a significant role in the N-acetylation of arylamines either in wild-type mice or in mice lacking Nat1 and Nat2 activities.

Key words: acetylation, acetyltransferases, carcinogen metabolism, drug clearance, phase II drug metabolism, transgenic models

This article has been cited by other articles:

				D. F. Barker, J. M. Walraven, E. H. Ristagno, M. A. Doll, J. C. States, and D. W. Hein Quantitative Tissue and Gene-Specific Differences and Developmental Changes in Nat1, Nat2, and Nat3 mRNA Expression in the Rat Drug Metab. Dispos., December 1, 2008; 36(12): 2445 - 2451. [Abstract] [Full Text] [PDF]

				D. W. Hein, J. Bendaly, J. R. Neale, and M. A. Doll Systemic Functional Expression of N-Acetyltransferase Polymorphism in the F344 Nat2 Congenic Rat Drug Metab. Dispos., December 1, 2008; 36(12): 2452 - 2459. [Abstract] [Full Text] [PDF]

				J. M. Walraven, D. F. Barker, M. A. Doll, and D. W. Hein Tissue Expression and Genomic Sequences of Rat N-acetyltransferases rNat1, rNat2, rNat3, and Functional Characterization of a Novel rNat3*2 Genetic Variant Toxicol. Sci., October 1, 2007; 99(2): 413 - 421. [Abstract] [Full Text] [PDF]