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MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Natriuretic peptides stimulate the cardiac sodium pump via NPR-C-coupled NOS activation

¹Northern Cardiac Research Group, Kolling Institute, University of Sydney, Sydney, ²Department of Cardiology, Gosford Hospital, Gosford, and ³Department of Cardiology, Royal North Shore Hospital, Sydney, Australia; and ⁴Medical Department, The Heart Centre, Rigshospitalet, National University Hospital, University of Copenhagen, Copenhagen, Denmark

Submitted 8 June 2007 ; accepted in final form 25 January 2008

Natriuretic peptides (NPs) and their receptors (NPRs) are expressed in the heart, but their effects on myocyte function are poorly understood. Because NPRs are coupled to synthesis of cGMP, an activator of the sarcolemmal Na⁺-K⁺ pump, we examined whether atrial natriuretic peptide (ANP) regulates the pump. We voltage clamped rabbit ventricular myocytes and identified electrogenic Na⁺-K⁺ pump current (arising from the 3:2 Na⁺:K⁺ exchange and normalized for membrane capacitance) as the shift in membrane current induced by 100 µmol/l ouabain. Ten nanomoles per liter ANP stimulated the Na⁺-K⁺ pump when the intracellular compartment was perfused with pipette solutions containing 10 mmol/l Na⁺ but had no effect when the pump was at near maximal activation with 80 mmol/l Na⁺ in the pipette solution. Stimulation was abolished by inhibition of cGMP-activated protein kinase with KT-5823, nitric oxide (NO)-activated guanylyl cyclase with 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ), or NO synthase with N^G-nitro-L-arginine methyl ester (L-NAME). Since synthesis of cGMP by NPR-A and NPR-B is not NO dependent or ODQ sensitive, we exposed myocytes to AP-811, a highly selective ligand for the NPR-C "clearance" receptor. It abolished ANP-induced pump stimulation. Conversely, the selective NPR-C agonist ANP(4-23) reproduced stimulation. The stimulation was blocked by L-NAME. To examine NO production in response to ANP(4-23), we loaded myocytes with the NO-sensitive fluorescent dye diacetylated diaminofluorescein-2 and examined them by confocal microscopy. ANP(4-23) induced a significant increase in fluorescence, which was abolished by L-NAME. We conclude that NPs stimulate the Na⁺-K⁺ pump via an NPR-C and NO-dependent pathway.

cyclic guanosine 3'; 5'-cyclic monophosphate-activated kinase; nitric oxide synthase; congestive cardiac failure; atrial natriuretic peptide

This article has been cited by other articles:

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