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Abstract
Hydralazine is used in the treatment of essential hypertension and is under investigation for epigenetic therapy in the treatment of neoplastic and renal diseases. N-acetyltransferase (NAT) 2 exhibits a common genetic polymorphism in human populations. After recombinant expression in yeast, human NAT2 exhibited an apparent Lineweaver-Burk constant (Km) value (20.1 ± 8.8 μM) for hydralazine over 20-fold lower than the apparent Km value (456 ± 57 μM) for recombinant human NAT1 (P = 0.0016). The apparent Vmax value for recombinant human NAT1 (72.2 ± 17.9 nmol acetylated/min/mg protein) was significantly (P = 0.0245) lower than recombinant human NAT2 (153 ± 15 nmol acetylated/min/mg protein), reflecting 50-fold higher clearance for recombinant human NAT2. Hydralazine NAT activities exhibited a robust acetylator gene dose response in cryopreserved human hepatocytes both in vitro and in situ. Hydralazine NAT activities in vitro differed significantly with respect to NAT2 genotype at 1000 (P = 0.0319), 100 (P = 0.002), and 10 μM hydralazine (P = 0.0029). Hydralazine NAT activities differed significantly (P < 0.001) among slow acetylator hepatocytes, (NAT2*5B/*5B > NAT2*5B/*6A > NAT2*6A/*6A). The in situ hydralazine N-acetylation rates differed significantly with respect to NAT2 genotype after incubation with 10 (P = 0.002) or 100 µM (P = 0.0015) hydralazine and were higher after incubation with 100 μM (10-fold) than with 10 μM (4.5-fold) hydralazine. Our results clearly document NAT2 genotype–dependent N-acetylation of hydralazine in human hepatocytes, suggesting that hydralazine efficacy and safety could be improved by NAT2 genotype–dependent dosing strategies.
Footnotes
- Received September 8, 2017.
- Accepted October 6, 2017.
This study was partially supported by US Public Health Service National Institutes of Health Grants [R25-CA134283 and P20-GM113226].
- Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics
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