Tier 3 — preclinical

Endothelium-derived relaxing factor produced and released from artery and vein is nitric oxide

Ignarro LJ, Buga GM, Wood KS, Byrns RE, Chaudhuri G
Proceedings of the National Academy of Sciences of the USA 1987 Volume 84, Issue 24, pages 9265-9269

Bibliography

PubMed
PMID 2827174
PubMed Central
PMC299734
DOI
10.1073/pnas.84.24.9265
Funding
Supported by NIH Grant HL35014 and the Laubisch Fund at the University of California, Los Angeles.

Study snapshot

DesignControlled laboratory bioassay/pharmacological comparison study
ModelIsolated perfused bovine intrapulmonary artery and vein; endothelium-denuded arterial/venous strips in cascade bioassay; freshly isolated aortic endothelial cells
SampleNot applicable (isolated tissue/bioassay study; N not reported as a subject count)
InterventionComparison of EDRF released from perfused vessels versus authentic NO gas delivered by superfusion; pharmacological inhibitors (pyrogallol, superoxide dismutase, oxyhemoglobin, potassium, methylene blue) and chemical detection (nitrosylhemoglobin formation, diazotization of sulfanilic acid)
DurationNot applicable (acute in vitro/ex vivo bioassay experiments)
EndpointsPharmacological comparability of EDRF and authentic NO (half-life, sensitivity to pyrogallol/superoxide, stabilization by SOD, inhibition by oxyhemoglobin/potassium); Comparable cyclic GMP accumulation induced by EDRF and NO, both inhibited by pyrogallol, oxyhemoglobin, potassium, and methylene blue; Chemical identification of EDRF as NO via nitrosylhemoglobin formation and diazotization of sulfanilic acid, matching the reaction products of authentic NO

What the study showed, in plain terms

This 1987 study by Louis Ignarro and colleagues is one of the two landmark papers (alongside a companion paper from Salvador Moncada's group published the same year) that proved a long-mysterious substance called "endothelium-derived relaxing factor" (EDRF) is actually nitric oxide (NO), a simple gas.

Since the late 1970s, researchers had known that blood vessel lining cells (endothelium) release a substance that relaxes surrounding smooth muscle, widening blood vessels, but its chemical identity was unknown. This study compared the biological behavior and chemical fingerprints of EDRF released from real blood vessels against pure nitric oxide gas, finding them indistinguishable in every test performed, including how quickly they degraded, which drugs blocked them, and what chemical byproducts they formed.

This finding resolved a major open question in cardiovascular biology and laid the groundwork for understanding how the body naturally regulates blood pressure, and how drugs like nitroglycerin have worked for over a century, ultimately contributing to Ignarro sharing the 1998 Nobel Prize in Physiology or Medicine.

Key findings

  • EDRF released from perfused bovine artery and vein and authentic NO were pharmacologically indistinguishable: both had a half-life of 3-5 seconds, were inactivated by pyrogallol or superoxide anion, stabilized by superoxide dismutase, and inhibited by oxyhemoglobin or potassium.
  • Both EDRF and NO produced comparable increases in cyclic GMP in artery and vein, and this response was blocked by the same set of inhibitors (pyrogallol, oxyhemoglobin, potassium, methylene blue).
  • EDRF released from freshly isolated aortic endothelial cells reacted with hemoglobin to form nitrosylhemoglobin, identical to the reaction seen with authentic NO.
  • EDRF and NO each similarly promoted diazotization of sulfanilic acid, yielding the same reaction product upon coupling with N-(1-naphthyl)-ethylenediamine, providing direct chemical confirmation that EDRF is NO or a closely related labile nitroso species.

What this study can and cannot tell us

This is a preclinical, ex vivo bioassay study using isolated bovine (not human) blood vessels and cultured endothelial cells, so direct extrapolation to intact human cardiovascular physiology requires corroboration from subsequent in vivo and human studies.

The chemical evidence, while strong, relies on indirect detection methods (nitrosylhemoglobin formation, diazotization) available at the time rather than direct real-time spectroscopic measurement of NO, which became possible only with later chemiluminescence-based techniques. No explicit competing-interest statement was reported in the source article.

Related papers in the corpus

Tier 3
The nature of endothelium-derived vascular relaxant factor
Griffith TM et al. · Nature · 1984
Tier 3
Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor
Palmer RM et al. · Nature · 1987
Tier 2
Nitric Oxide: A Unique Endogenous Signaling Molecule in Vascular Biology (Nobel Lecture)
Ignarro LJ et al. · Angewandte Chemie International Edition · 1999
Tier 2
Nitric oxide as a unique signaling molecule in the vascular system: a historical overview
Ignarro LJ et al. · Journal of Physiology and Pharmacology · 2002

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction Dr. Amr Yasser, PhDCardiometabolic, Musculoskeletal, Gut & Bioavailability Dr. Abdulla Mostafa, PhDCellular Senescence, Neurological, Mitochondrial & Brain-Ageing Biology