Positive inotropic and negative chronotropic effects of proton pump inhibitors in isolated rat atrium
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Updated: Aug 16, 2026

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
Published on: September 17, 2015
Aydan Yenisehirli1, Rustu Onur
1Department of Pharmacology, Faculty of Medicine, Gaziosmanpasa University, Tokat 60100, Turkey. aydany@hacettepe.edu.tr
Abstract:
The effects of three specific H+/K+-ATPase inhibitors (omeprazole, lansoprazole and SCH 28080 (2-methyl-8-(phenylmethoxy)-imidazo[1,2-a] pyridine-3-acetonitrile)) were investigated on the mechanical and electrophysiological properties of rat atrium, in vitro. Omeprazole (100-300 microM), lansoprazole (100-300 microM) and SCH 28080 (10-100 microM) increased the amplitude of contractions and decreased the beating rate. These effects are reversible, reproducible and correlated with their order of potency as gastric H+/K+-ATPase inhibitors; SCH 28080 > omeprazole = lansoprazole. Cardiac effects of proton pump inhibitors were not inhibited with phentolamine (5 microM), propranolol (15 microM), atropine (1 microM), ouabain (2 microM), theophylline (300 microM) and milrinone (100 microM). Ouabain-induced increase in beating rate and contracture development were antagonized by H+/K+-ATPase inhibitors. Ouabain increased the positive inotropic effect of H+/K+-ATPase inhibitors. Lansoprazole (300 microM) significantly prolonged the duration of action potentials in rat atrial cells. H+/K+-ATPase may play a crucial role in the mechanical and electrophysiological properties of rat atrial myocardium.
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