Tier 2 — strong

Nitric oxide as a unique signaling molecule in the vascular system: a historical overview

Ignarro LJ
Journal of Physiology and Pharmacology 2002 Volume 53, Issue 4, pages 503-514

Bibliography

PubMed
PMID 12512688

Study snapshot

DesignNarrative historical review of basic and clinical research on NO and cyclic GMP in vascular biology, first-person account by Louis Ignarro.
ModelSynthesis spanning isolated bovine coronary artery, purified/heme-reconstituted soluble guanylyl cyclase, human platelets, and rabbit/canine/human corpus cavernosum tissue.
SampleNarrative review of the author's cumulative research program; no single study population.
InterventionN/A (review) — covers NO gas, nitroglycerin and nitrovasodilators, S-nitrosothiols, and NOS-derived endogenous NO.
DurationCovers approximately 25 years of research, from the 1979 discovery of NO's vasorelaxant properties through 2002.
EndpointsVascular smooth muscle relaxation; Guanylyl cyclase activation and cyclic GMP formation; Platelet aggregation inhibition; Basal and shear-stress-dependent NO generation and systemic blood pressure regulation; Corpus cavernosum relaxation and erectile function

What the study showed, in plain terms

This is a first-person historical review by Louis Ignarro, one of the scientists who identified nitric oxide (NO) as the long-sought "endothelium-derived relaxing factor" that blood vessels use to relax and widen. Ignarro traces the field from 1979, when his lab showed that NO gas itself relaxes coronary artery tissue, through the discovery that nitroglycerin (a heart medication used for over a century) works by releasing NO in the body.

The review explains how NO activates an enzyme called guanylyl cyclase inside vascular smooth muscle cells, raising levels of a second messenger (cyclic GMP) that causes the muscle to relax. It also covers the discovery that the body's own cells manufacture NO continuously, that shear stress from flowing blood triggers this production, and that NO independently blocks platelet clumping, protecting against clot formation.

Finally, the review describes NO's role as a neurotransmitter, including the finding that NO released from nerves in the penis mediates erection, work that underpinned the development of sildenafil (Viagra). Ignarro closes by arguing that defects in the NO-cyclic GMP pathway likely contribute to many cardiovascular diseases and that NO-based drugs hold promise for treating them.

Key findings

  • 1979: NO gas was shown to be a potent relaxant of bovine coronary artery and to activate soluble guanylyl cyclase, one year before endothelium-dependent relaxation and EDRF were discovered.
  • Nitroglycerin, organic nitrate/nitrite esters, and nitroprusside relax vascular smooth muscle by undergoing metabolic conversion to NO, largely via intermediate S-nitrosothiols formed from reaction with tissue thiols.
  • NO activates guanylyl cyclase via a heme-dependent mechanism, forming a nitrosyl-heme complex that increases the enzyme's maximal velocity roughly 100-fold and decreases its Km for GTP roughly 3-fold.
  • EDRF was definitively identified as NO in 1987, resolving nearly a decade of parallel research threads on exogenous NO donors and endogenous EDRF.
  • Vascular endothelial cells continuously generate basal NO, triggered by shear stress from blood flow; inhibiting NO synthase in animals causes a prompt, sustained rise in systemic blood pressure.
  • NANC neurons release NO as the primary neurotransmitter mediating penile erection in rabbit, canine, and human corpus cavernosum, providing the mechanistic basis for phosphodiesterase-5 inhibitor drugs such as sildenafil.

What this study can and cannot tell us

This is a first-person narrative historical review rather than a systematic review or primary dataset, so it reflects the author's own selective framing and recollection of discoveries he was directly involved in.

The review synthesizes findings across many prior studies (including the author's own primary papers) without independent re-analysis or quantitative meta-analytic synthesis, and no explicit funding source or competing-interest disclosure was provided 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 3
Endothelium-derived relaxing factor produced and released from artery and vein is nitric oxide
Ignarro LJ et al. · Proceedings of the National Academy of Sciences of the USA · 1987
Tier 2
Nitric Oxide: A Unique Endogenous Signaling Molecule in Vascular Biology (Nobel Lecture)
Ignarro LJ et al. · Angewandte Chemie International Edition · 1999

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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