Figure 3.

Propranolol acts as an MBI of dextrorphan (DOR) formation in TG and WT mouse liver microsomes in vitro. Dixon (a and b) and IC₅₀ plots (c and d) of dextrorphan formation by pooled TG (a and c) and WT (b and d) mouse liver microsomes. In (a) and (b), pooled TG or WT mouse liver microsomes (0.1 mg·ml⁻¹) were incubated with propranolol (0–50 nM) for 5 min before 2.5, 5, or 10 μM of dextromethorphan (DEX) was added. In (c) and (d), pooled TG or WT mouse liver microsomes (0.1 mg·ml⁻¹) were incubated with propranolol (0–100 μM), with or without NADPH, for 5 min before dextromethorphan (5 µM) was added. The difference in dextrorphan formation between propranolol preincubation, with and without NADPH, before the dextromethorphan was added, suggests that propranolol acts as an MBI of CYP2D in liver microsomes from TG (c) and WT mice (d)