Table 4

Apparent V_max (nmol/min/g liver) and K_M (nM) for metoprolol metabolism, α-hydroxylation, and O-demethylation estimated by nonlinear curve-fitting based on the assumptions of the well-stirred and parallel tube models

	Condition	V_max ± SD	K_M ± SD	R
		nmol/min/g liver	nM
Well-stirred model
Metoprolol	Control	38.2 ± 7.2	3,590 ± 552	0.888
	AA	19.0 ± 4.0^4-a	4,483 ± 744	0.841
α-Hydroxymetoprolol	Control	23.6 ± 4.0	3,975 ± 552	0.918
	AA	11.1 ± 2.4^4-a	3,940 ± 716	0.796
O-Demethylmetoprolol	Control	7.5 ± 1.2	7,454 ± 1,192	0.930
	AA	3.5 ± 0.4^4-a	5,559 ± 836	0.892
Parallel tube model
Metoprolol	Control	45.6 ± 15.6	8,770 ± 1,428	0.920
	AA	20.7 ± 3.2^4-a	6,964 ± 948	0.870
α-Hydroxymetoprolol	Control	27.0 ± 8.4	8,935 ± 6,652	0.938
	AA	11.9 ± 136	6,053 ± 30,236	0.826
O-Demethylmetoprolol	Control	10.0 ± 1.2	19,497 ± 2,132	0.955
	AA	3.9 ± 1.6^4-a	8,863 ± 6,564	0.913

↵4-a p < 0.05, controlvs. amino acids (AA).