PT - JOURNAL ARTICLE AU - Cecily E Allen AU - Mark A Doll AU - David W Hein TI - N-acetyltransferase 2 Genotype-dependent N-acetylation of Hydralazine in Human Hepatocytes AID - 10.1124/dmd.117.078543 DP - 2017 Jan 01 TA - Drug Metabolism and Disposition PG - dmd.117.078543 4099 - http://dmd.aspetjournals.org/content/early/2017/10/10/dmd.117.078543.short 4100 - http://dmd.aspetjournals.org/content/early/2017/10/10/dmd.117.078543.full AB - Hydralazine is used in treatment of essential hypertension and is under investigation for epigenetic therapy in the treatment of neoplastic and renal diseases. N-acetyltransferase 2 (NAT2) exhibits a common genetic polymorphism in human populations. Following recombinant expression in yeast, human NAT2 exhibited an apparent Km (20.1 ± 8.8 μM) for hydralazine over 20-fold lower than the apparent Km (456 ± 57 μM) for recombinant human NAT1 (p=0.0016). The apparent Vmax for recombinant human NAT1 (72.2 ± 17.9 nmoles acetylated/min/mg protein) was significantly (p=0.0245) lower than recombinant human NAT2 (153 ± 15 nmoles acetylated/min/mg protein) reflecting 50-fold higher clearance for recombinant human NAT2. Hydralazine N-acetyltransferase activities exhibited a robust acetylator gene dose-response in cryopreserved human hepatocytes both in vitro and in situ. Hydralazine N-acetyltransferase activities in vitro differed significantly with respect to NAT2 genotype at 1000 μM (p=0.0319); 100 μM (p=0.002); and 10 μ;M hydralazine (p=0.0029). Hydralazine N-acetyltransferase 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 following incubation with 10 μM (p=0.002) or 100 μM (p=0.0015) hydralazine and were higher following incubation with 100 μM (10-fold) than 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.