Expression of H(+)/K(+)-ATPase was recently shown in cardiac and vascular muscle cells and significant inotropic, chronotropic and vasorelaxant effects of proton pump inhibitors were also previously shown on isolated cardiac and vascular muscles. We aimed to study possible reflections of these in vitro effects on a living animal and thus we investigated the effects of intravenously administered omeprazole (7.2 mg/kg), lansoprazole (7.7 mg/kg) and pantoprazole (9 mg/kg) on blood pressure and electrocardiogram in anesthetized rat. None of the three tested inhibitors altered heart rate, blood pressure or electrocardiogram recording in anesthetized rat even at 100-fold greater plasma concentrations than in clinical settings. Inotropic effects of omeprazole and lansoprazole were also tested on electrically induced contractions of human atrial strips and they induced a concentration-dependent, completely reversible and reproducible negative inotropic effect on isolated human myocardium. Both inhibitors further increased the tension of human atrial strips when they applied after the development of ouabain-induced "contracture". This study demonstrates cardiovascular safety of three most commonly used proton pump inhibitors in anesthetized rat. In contrast to in vitro studies, proton pump inhibitors were found to be ineffective in cardiovascular system in vivo and this may be due to high plasma protein binding and rapid elimination rates. Contrary to previous findings on isolated rat atrium, omeprazole and lansoprazole induced negative inotropic effect on isolated human atrial strips.