Contractile dysfunction and diminished response to -adrenergic agonists are characteristics for failing hearts. Chemically donated nitroxyl (HNO) improves contractility in failing hearts and thus may have therapeutic potential. Yet, there is a need for pharmacologically suitable donors. In this study we tested whether the pure and long acting HNO donor, 1-nitrosocyclohexyl acetate (NCA), affects contractile force in normal and pathological ventricular myocytes (VMs) as well as in isolated hearts. VMs were isolated from mice either subjected to isoprenaline-infusion (ISO; 30 g/g per day) or to vehicle (0.9% NaCl) for 5 days. Sarcomere shortening and Ca2+ transients were simultaneously measured using the IonOptix system. Force of contraction of isolated hearts was measured by a Langendorff-perfusion system. NCA increased peak sarcomere shortening by+40-200% in a concentration-dependent manner (EC50 55 M). Efficacy and potency did not differ between normal and chronic ISO VMs, despite the fact that the latter displayed a markedly diminished inotropic response to acute -adrenergic stimulation with ISO (1 M). NCA (60 M) increased peak sarcomere shortening and Ca2+ transient amplitude by 200% and 120%, respectively, suggesting effects on both myofilament Ca2+ sensitivity and sarcoplasmic reticulum (SR) Ca2+ cycling. Importantly, NCA did not affect diastolic Ca2+ or SR Ca2+ content, as assessed by rapid caffeine application. NCA (45 M) increased force of contraction by 30% in isolated hearts. In conclusion, NCA increased contractile force in normal and -adrenergically desensitized VMs as well as in isolated mouse hearts. This profile warrants further investigations of this HNO donor in the context of heart failure.
Contractile dysfunction and diminished response to -adrenergic agonists are characteristics for failing hearts. Chemically donated nitroxyl (HNO) improves contractility in failing hearts and thus may have therapeutic potential. Yet, there is a need for pharmacologically suitable donors. In this study we tested whether the pure and long acting HNO donor, 1-nitrosocyclohexyl acetate (NCA), affects contractile force in normal and pathological ventricular myocytes (VMs) as well as in isolated hearts. VMs were isolated from mice either subjected to isoprenaline-infusion (ISO; 30 g/g per day) or to vehicle (0.9% NaCl) for 5 days. Sarcomere shortening and Ca2+ transients were simultaneously measured using the IonOptix system. Force of contraction of isolated hearts was measured by a Langendorff-perfusion system. NCA increased peak sarcomere shortening by+40-200% in a concentration-dependent manner (EC50 55 M). Efficacy and potency did not differ between normal and chronic ISO VMs, despite the fact that the latter displayed a markedly diminished inotropic response to acute -adrenergic stimulation with ISO (1 M). NCA (60 M) increased peak sarcomere shortening and Ca2+ transient amplitude by 200% and 120%, respectively, suggesting effects on both myofilament Ca2+ sensitivity and sarcoplasmic reticulum (SR) Ca2+ cycling. Importantly, NCA did not affect diastolic Ca2+ or SR Ca2+ content, as assessed by rapid caffeine application. NCA (45 M) increased force of contraction by 30% in isolated hearts. In conclusion, NCA increased contractile force in normal and -adrenergically desensitized VMs as well as in isolated mouse hearts. This profile warrants further investigations of this HNO donor in the context of heart failure.