RT Journal Article
SR Electronic
T1 Electron Spin Resonance and Chemiluminescence Analyses to Elucidate the Vasodilating Mechanism of Sodium Nitroprusside
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1672
OP 1680
DO 10.1124/mol.106.027870
VO 70
IS 5
A1 Giancarlo Aldini
A1 Federica Pirrone
A1 Mariangela Albertini
A1 Marica Orioli
A1 Angela Piccoli
A1 Silvia Mazzola
A1 Maria Giovanna Clement
A1 Marina Carini
YR 2006
UL http://molpharm.aspetjournals.org/content/70/5/1672.abstract
AB The aim of this study was to elucidate the vasodilating mechanism of sodium nitroprusside (SNP). To do this, SNP was intravenously infused in pigs (1.67 μmol/kg), and the following paramagnetic metabolites were identified by electron spin resonance: 1) nitrosylhemoglobin [HbFe(II)NO] as an index of the bioconservative pathway; 2) transferrin; 3) [Fe(II)(CN)5 NO]3- and [Fe(II)(CN)4 NO]2-, the reduced penta- and tetracoordinated intermediates of SNP, respectively; and 4) methemoglobin (met-Hb). The results indicate the following: 1) ≈17% of the dose is converted to HbFe(II)NO at the end of infusion; 2) NO administered as SNP does not undergo bioinactivation (oxidative metabolism), because no significant increase of met-Hb was observed; 3) the equilibrium involving the paramagnetic species of SNP is shifted toward HbFe(II)NO, because a significant increase of transferrin but no detection of the reduced paramagnetic intermediates of SNP was observed. The results obtained indicate that the hemodynamic effect induced by SNP is not mediated by HbFe(II)NO, at least under physiological conditions; hence, a direct release of NO from SNP in the vascular target should be considered. To demonstrate this mechanism, endothelial cells were incubated with SNP, and the release of NO was determined by a novel chemiluminescence method. The results indicate that the endothelium is able to metabolize SNP, with the formation of stoichiometric amounts of NO. In conclusion, SNP is rapidly metabolized to HbFe(II)NO, but the pharmacological response is mediated by a direct mechanism of NO release of the parent compound at the cellular target. The American Society for Pharmacology and Experimental Therapeutics