We tested the hypothesis that intracoronary injection of a recombinant adenovirus encoding adenylyl cyclase type VI (AC(VI)) would increase cardiac function in pigs. Left ventricular (LV) dP/dt and cardiac output in response to isoproterenol and NKH477 stimulation were assessed in normal pigs before and 12 days after intracoronary delivery of histamine followed by intracoronary delivery of an adenovirus encoding lacZ (control) or AC(VI) (1.4x10(12) vp). Animals that had received AC(VI) gene transfer showed increases in peak LV dP/dt (average increase of 1267+/-807 mm Hg/s; P=0.0002) and cardiac output (average increase of 39+/-20 mL. kg(-1). min(-1); P<0.0001); control animals showed no changes. Increased LV dP/dt was evident 6 days after gene transfer and persisted for at least 57 days. Basal heart rate, blood pressure, and LV dP/dt were unchanged, despite changes in cardiac responsiveness to catecholamine stimulation. Twenty-three hour ECG recordings showed no change in mean heart rate or ectopic beats and no arrhythmias. LV homogenates from animals receiving AC(VI) gene transfer showed increased AC(VI) protein content (P=0.0007) and stimulated cAMP production (P=0.0006), confirming transgene expression and function; basal LV AC activity was unchanged. Increased cAMP-generating capacity persisted for at least 18 weeks (P<0.0002). Intracoronary injection of a recombinant adenovirus encoding AC provides enduring increases in cardiac function.