A cAMP-dependent PDE3 inhibitor (IC50s = 0.04 and 0.03 nM for PDE3A and PDE3B, respectively in T84 cell lysates); stimulates cAMP accumulation (10 μM) and increases membrane capacitance in rat juxtaglomerular cells; competitively inhibits multidrug resistant protein 5-mediated export of cGMP from Chinese hamster lung fibroblasts (Ki = 240 nM); reduces collagen-induced platelet aggregation in rabbits (3 μg/kg per minute); reduces collagen-induced decreases in mean arterial blood pressure alone or in combination with prostacyclin