Amyloid beta peptide 22-35 induces a negative inotropic effect on isolated rat hearts

Evidences indicate that deposition of amyloid beta peptides (Aβs) plays an important role in the pathogenesis of Alzheimer disease. Aβs may influence cardiovascular system and ileum contractions. But the effect of amyloid beta peptide 22-35 (Aβ_22-35) on cardiovascular functions and contractions of ileum has not been studied. Therefore, the present study aimed to investigate the possible effects of this peptide on isolated rat heart and ileum smooth muscle. Langendorff-perfused rat heart preparations were established. The hearts were perfused under constant pressure (60 mmHg) with modified Krebs-Henseleit solution. Aβ_22-35 at doses of 1, 10 and 100 nM significantly decreased left ventricular developed pressure (LVDP; an index of cardiac contractility) and maximal rate of pressure development of left ventricle (+dP/dt_max; another index of cardiac contractility). This peptide at doses studied had no significant effect on heart rate, coronary flow, monophasic action potential amplitude (MAPamp), MAP duration at 90% repolarization (MAP₉₀) and ileum contractions. We suggest that Aβ_22-35 exerts a negative inotropism on isolated rat hearts with unchanged heart rate, coronary flow, MAPamp, MAP₉₀ and smooth muscle contractility of ileum.