Definitive role for natriuretic peptide receptor-C in mediating the vasorelaxant activity of C-type natriuretic peptide and endothelium-derived hyperpolarising factor.
OBJECTIVE
C-type natriuretic peptide (CNP) has recently been suggested to represent an endothelium-derived hyperpolarising factor (EDHF) in the mammalian resistance vasculature and, as such, important in the regulation of local blood flow and systemic blood pressure. Additionally, this peptide has been shown to protect against ischaemia-reperfusion injury and inhibits leukocyte and platelet activation. Herein, we use a novel, selective natriuretic peptide receptor-C (NPR-C) antagonist (M372049) to highlight the pivotal contribution of CNP/NPR-C signalling in the EDHF-dependent regulation of vascular tone and investigate the mechanism(s) underlying the release and biological activity of CNP.


METHODS
In vitro pharmacological investigation was conducted in rat (Sprague-Dawley) aorta and mesenteric resistance arteries. Relaxant responses to CNP, atrial natriuretic peptide (ANP), the nitric oxide donor spermine-NONOate (SPER-NO) and the endothelium-dependent vasodilator, acetylcholine (ACh) were examined in the absence and presence of M372049 or inhibitor cocktails shown previously to block endothelium-dependent dilatation in the resistance vasculature. RT-PCR was employed to characterize the expression of NPR subtypes in the vessels studied.


RESULTS
M372049 produced concentration-dependent inhibition of the vasorelaxant activity of CNP in rat isolated mesenteric resistance arteries but not aorta; in contrast, M372049 did not affect relaxations to ANP or SPER-NO in either vessel. M372049 or ouabain alone produced small, significant inhibition of EDHF-dependent relaxations in mesenteric arteries and in combination acted synergistically to abolish such responses. A combination of M372049 with established inhibitors of EDHF-dependent relaxation revealed that multiple, distinct pathways coordinate the bioactivity of EDHF in the resistance vasculature, and that CNP/NPR-C signalling represents a major component.


CONCLUSIONS
These data substantiate CNP/NPR-C signalling as a fundamental pathway underlying EDHF-dependent regulation of vascular tone in the rat mesenteric resistance vasculature. An increased understanding of the physiological roles of CNP/NPR-C signalling in the vasculature (now facilitated by the identification of a selective NPR-C antagonist) should aid determination of the (patho)physiological importance of EDHF and might provide the rationale for the design of novel therapeutics.
Villar
Inmaculada C
IC
Clinical Pharmacology, William Harvey Research Institute, Bart's and The London, Charterhouse Square, London EC1M 6BQ, UK.
Panayiotou
Catherine M
CM
Sheraz
Adil
A
Madhani
Melanie
M
Scotland
Ramona S
RS
Nobles
Muriel
M
Kemp-Harper
Barbara
B
Ahluwalia
Amrita
A
Hobbs
Adrian J
AJ
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D001685:Biological Factors / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries; D020098:Natriuretic Peptide, C-Type / Q000494:pharmacology*; D009842:Oligopeptides / Q000494:pharmacology*; D010042:Ouabain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects; D011720:Pyrazoles / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017461:Receptors, Atrial Natriuretic Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013096:Spermine / Q000031:analogs & derivatives / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
D001685:Biological Factors; C522718:M 372049; D009842:Oligopeptides; D015221:Potassium Channels; D011720:Pyrazoles; D011810:Quinoxalines; C411671:TRAM 34; D014665:Vasodilator Agents; C067410:endothelium-dependent hyperpolarization factor; D020098:Natriuretic Peptide, C-Type; C091861:spermine nitric oxide complex; D001464:Barium; D013096:Spermine; D010042:Ouabain; D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor; C073616:atrial natriuretic factor receptor C; D000254:Sodium-Potassium-Exchanging ATPase; D000109:Acetylcholine