Table 2

Determination of the K_m and V_maxfor bufuralol 1′ hydroxy formation by human liver microsome lots HL-1008 and HL-1062-2 in the presence of quinidine and S-mephenytoin

Inhibitor	K_m	V_max	CI_int
	μM	nmol/min/mg	ml/min/mg protein
HL-1008
Methanol (1%)^1-a	14	0.060	0.004
Quinidine (1 μM)	38	0.051	0.001
HL-1062-2
Methanol (2%)^1-b	15	0.240	0.016
1 μM Quinidine + 50 μM S-Mephenytoin	145	0.248	0.002

Method: Bufuralol concentrations ranging from 0.5 to 500 μM were incubated with human liver microsome lots HL-1008 (0.16 mg) and HL-1062-2 (0.12 mg) for 20 min in the presence of methanol, quinidine,S-mephenytoin, or a combination (methanol evaporated prior to incubation). Data for K_m andV_max taken from Eadie-Hofstee plots as described inMaterials and Methods.

↵1-a Control for 1 μM Quinidine.
↵1-b Control for 1 μM Quinidine + 50 μMS-Mephenytoin.