Key result
NOS3 knockout ventricular myocytes exhibit prolonged action potential duration during beta-adrenergic stimulation without differences in potassium currents, likely due to increased SR calcium load.
Why the study?
Are prolonged action potentials and afterdepolarizations in NOS3-deficient ventricular myocytes due to altered potassium currents during β-adrenergic stimulation?
Are prolonged action potentials and afterdepolarizations in NOS3-deficient ventricular myocytes due to altered potassium currents during β-adrenergic stimulation?
Answers are grounded in this paper and cite their sources.
Prolonged action potentials and increased spontaneous activity in NOS3-deficient ventricular myocytes during β-adrenergic stimulation are likely driven by increased SR Ca2+ load rather than altered potassium currents.
Ventricular myocytes deficient in endothelial nitric oxide synthase (NOS3(-/-)) exhibit prolonged action potential (AP) duration and enhanced spontaneous activity (early and delayed afterdepolarizations) during β-adrenergic (β-AR) stimulation. Studies have shown that nitric oxide is able to regulate various K(+) channels. Our objective was to examine if NOS3(-/-) myocytes had altered K(+) currents. APs, transient outward (I(to)), sustained (I(Ksus)), and inward rectifier (I(K1)) K(+) currents were measured in NOS3(-/-) and wild-type (WT) myocytes. During β-AR stimulation, AP duration (measured as 90% repolarization-APD(90)) was prolonged in NOS3(-/-) compared to WT myocytes. Nevertheless, we did not observe differences in I(to), I(Ksus), or I(K1) between WT and NOS3(-/-) myocytes. Our previous work showed that NOS3(-/-) myocytes had a greater Ca(2+) influx via L-type Ca(2+) channels with β-AR stimulation. Thus, we measured β-AR-stimulated SR Ca(2+) load and found a greater increase in NOS3(-/-) versus WT myocytes. Hence, our data suggest that the prolonged AP in NOS3(-/-) myocytes is not due to changes in I(to), I(Ksus), or I(K1). Furthermore, the increase in spontaneous activity in NOS3(-/-) myocytes may be due to a greater increase in SR Ca(2+) load. This may have important implications for heart failure patients, where arrhythmias are increased and NOS3 expression is decreased.
No takes yet. Share an insight, caveat, or question.
Wang et al. (2012) studied NOS3 deficiency. NOS3 knockout (NOS3(-/-)) vs. Wild-type (WT) was evaluated on Potassium currents (I(to), I(Ksus), I(K1)) and action potential duration. NOS3 knockout ventricular myocytes exhibit prolonged action potential duration during beta-adrenergic stimulation without differences in potassium currents, likely due to increased SR calcium load.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: