C-Type Natriuretic peptide (CNP) release does not contribute to endothelium-derived hyperpolarizing factor (EDHF) mediated relaxation in porcine coronary artery

Abstract

Objective: The release of CNP accounts for EDHF-mediated relaxations in the rat mesenteric artery1 and is Gi protein dependent2. EDHF-mediated relaxations in the porcine coronary artery are not Gi dependent3. This study investigates whether or not CNP release accounts for EDHF-responses in this artery. Methods: (1) CNP concentration was measured by enzyme immunoassay in bathing solution containing porcine coronary arterial rings where EDHF response was initiated by bradykinin (100 nM). (2) EDHF-mediated relaxations induced by SFLLRN were compared with those to exogenous CNP in the presence of phosphoramidon (10 µM; known to potentiate CNP induced relaxations). Results: There was no significant difference in the CNP concentrations between chambers containing rings that did or did not exhibit a EDHF-mediated response. Relaxations induced by CNP alone were potentiated by phosphoramidon (maximal relaxation 60.7 ± 7.7 % vs 84.1 ± 7.5 %, control vs phosphoramidon, P<0.05) but the EDHF-mediated responses to SFLLRN were not (maximal relaxation 69.9 ± 9.1 % vs 72.8 ± 9.9 %, control vs phosphoramidon) Conclusions: Unlike in the mesenteric artery and the heart of the rat, CNP release does not contribute to EDHF-mediated relaxations in the porcine coronary artery. FOOTNOTES Support: HKU CRCG (No. 21374077) REFERENCES Villar , et al. Cardiovasc Res 2007914.3 Chauhan , et al. PNAS 2003914.3 Ng , et al. J Vasc Res 200512 S201