Does nitric oxide mediate the vasodilator activity of nitroglycerin?
Nitroglycerin (glyceryl trinitrate, GTN) relaxes blood vessels primarily via activation of the soluble guanylyl cyclase (sGC)/cGMP/cGMP-dependent protein kinase (cGK-I) pathway. Although the precise mechanism of sGC activation by GTN in the vascular wall is unknown, the mediatory role of nitric oxide (NO) has been postulated. We tested the GTN/NO hypothesis in different types of isolated rat and rabbit blood vessels using two novel approaches: (1) EPR spin trapping using colloid Fe(DETC)2 and (2) analysis of cGK-I-dependent phosphorylation of the vasodilator-stimulated phosphoprotein at Ser239 (P-VASP). For comparison, another organic nitrate, isosorbide dinitrate (ISDN), and endothelium-dependent vasodilator, calcium ionophore A23187, were tested. We found a marked discrepancy between GTN's strong vasoactivity (vasodilation and augmentation of P-VASP) and its poor NO donor properties. In aortas precontracted with phenylephrine, GTN, ISDN, and A23187 induced nearly full relaxations (>80%) and doubling of vascular P-VASP content at concentrations of 100 nmol/L, 100 micromol/L, and 1 micromol/L, respectively. GTN applied in vasorelaxant concentrations (10 to 1000 nmol/L) did not significantly increase the basal vascular NO production, in contrast to ISDN and A23187. The absence of GTN-derived NO was confirmed in rabbit vena cava and renal artery. A significant increase in vascular NO formation was observed only at suprapharmacological GTN concentrations (>10 micromol/L). The concentration dependency of NO formation from GTN was comparable to that of ISDN, although the latter exhibits 100-folds lower vasorelaxant potency. We conclude that GTN activates the sGC/cGMP/cGK-I pathway and induces vasorelaxation without intermediacy of the free radical NO. The full text of this article is available online at http://www.circresaha.org.
Kleschyov
Andrei L
AL
Division of Cardiology, University Hospital Hamburg-Eppendorf, Martinistr 52, Hamburg 20246, Germany. kleschyo@uke.uni-hamburg.de
Oelze
Matthias
M
Daiber
Andreas
A
Huang
Yale
Y
Mollnau
Hanke
H
Schulz
Eberhard
E
Sydow
Karsten
K
Fichtlscherer
Birgit
B
Mülsch
Alexander
A
Münzel
Thomas
T
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D001542:Benomyl / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D015815:Cell Adhesion Molecules / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D007548:Isosorbide Dinitrate / Q000494:pharmacology; D008297:Male; D008840:Microfilament Proteins; D009569:Nitric Oxide / Q000378:metabolism*; D005996:Nitroglycerin / Q000494:pharmacology*; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012077:Renal Artery / Q000187:drug effects / Q000502:physiology; D000071756:Soluble Guanylyl Cyclase; D019097:Spin Trapping; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology*; D014684:Venae Cavae / Q000187:drug effects / Q000502:physiology; D000098662:Vasodilator-Stimulated Phosphoprotein
D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D007476:Ionophores; D008840:Microfilament Proteins; D010750:Phosphoproteins; D018160:Receptors, Cytoplasmic and Nuclear; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D000098662:Vasodilator-Stimulated Phosphoprotein; D009569:Nitric Oxide; D000001:Calcimycin; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D005996:Nitroglycerin; D007548:Isosorbide Dinitrate; D001542:Benomyl