Abstract
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a heterocyclic amine identified in the human diet and in cigarette smoke that produces prostate tumors in the rat. PhIP is bioactivated by cytochrome P-450 enzymes to N-hydroxylated metabolites that undergo further activation by conjugation enzymes, including theN-acetyltransferases, NAT1 and NAT2. To investigate the role of prostate-specific expression of human N-acetyltransferase 2 (NAT2) on PhIP-induced prostate cancer, we constructed a transgenic mouse model that targeted expression of human NAT2 to the prostate. Following construction, prostate, liver, lung, colon, small intestine, urinary bladder, and kidney cytosols were tested for human NAT1- and NAT2-specific N-acetyltransferase activities. Human NAT2-specific N-acetyltransferase activities were 15-fold higher in prostate of transgenic mice versus control mice, but were equivalent between transgenic mice and control mice in all other tissues tested. Human NAT1-specific N-acetyltransferase activities did not differ between transgenic and control mice in any tissue tested. Prostate cytosols from transgenic and control mice did not differ in their capacity to catalyze the N-acetylation of 2-aminofluorene, the O-acetylation ofN-hydroxy-2-aminofluorene andN-hydroxy-PhIP or theN,O-acetylation ofN-hydroxy-2-acetylaminofluorene. Transgenic and control mice administered PhIP did not differ in PhIP-DNA adduct levels in the prostate. This study is the first to report transgenic expression of human NAT2 in the mouse. The results do not support a critical role for bioactivation of heterocyclic amine carcinogens by humanN-acetyltransferase-2 in the prostate. However, the lack of an effect may relate to the level of overexpression achieved and the presence of endogenous mouse acetyltransferases and/or sulfotransferases.
Footnotes
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Send reprint requests to: David W. Hein, Ph.D., Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY 40292. E-mail:d.hein{at}louisville.edu
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↵1 This work was partially supported by United States Public Health Service Grant CA34627 from the National Cancer Institute. A preliminary report of this work was presented at the 1998 annual meeting of the Society of Toxicology (Leff et al., 1998; Toxicol Sci42:318).
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↵2 This work constitutes partial fulfillment by Matthew Leff for the Ph.D. in Pharmacology and Toxicology at the University of Louisville.
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↵3 Present address: Toxicology and Pathology Services, Inc., 10424 Middle Mount Vernon Rd., Mt. Vernon, IN 47620.
- Abbreviations:
- PhIP
- 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine
- NAT2
- N-acetyltransferase 2
- NAT1
- N-acetyltransferase 1
- SMZ
- sulfamethazine
- PABA
- p-aminobenzoic acid
- PB
- probasin
- PCR
- polymerase chain reaction
- bp
- base pair
- AF
- 2-aminofluorene
- DTT
- dithiothreitol
- Received December 29, 1998.
- Accepted March 23, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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