150 µg pGL4 mixed with 10 Vol% or sham Definity® was injected through a portal vein branch into the medial lobe of rat liver for 45 sec, with initially coincident or sham US exposure (1.1 MHz, 2.7 MPa peak negative pressure, 20 cycle pulses, 13.9 Hz PRF), which continued after injection for a total acoustic exposure time of 90 sec. Luciferase expression was measured in extracts from the treated lobe. Error bars indicate SEM (n=6).