Table 2

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

μM nmol/min/mg ml/min/mg protein
 Methanol (1%)1-a 140.0600.004
 Quinidine (1 μM)380.0510.001
 Methanol (2%)1-b 150.2400.016
 1 μM Quinidine + 50  μM S-Mephenytoin1450.2480.002

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 Km andVmax 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.