7 Blood Vessel Changes Linked to Reduced Nitric Oxide

Nitric oxide is best known for helping blood vessels relax and widen. But that is only one of its jobs. It is made by the thin layer of cells that lines the inside of every blood vessel, and from there it also helps keep blood cells from sticking, keeps the vessel wall from thickening and helps arteries stay flexible.

So when the body makes less nitric oxide, the effects show up in more than one place. Some changes happen in the lining itself, some in the muscle of the vessel wall, and some in the blood flowing past.

Here are seven of those changes, and how each one happens.

1. The Inner Lining Gets Stickier

Nitric oxide helps regulate how white blood cells interact with the inside of blood vessels. When there is less of it, white blood cells can become more likely to cling to the vessel wall. In an animal study, blocking nitric oxide production increased white blood cell adhesion more than 15-fold and also increased their movement through the vessel lining. This shows how reduced nitric oxide can make the endothelium more adhesive and inflammatory. [1]

2. Platelets Clump Together More Easily

Platelets are tiny cells in your blood that clump together to stop bleeding when you get a cut. Nitric oxide released by the vessel lining helps inhibit platelet aggregation while blood is circulating normally. Research has also shown that nitric oxide can help break apart platelets that have already begun aggregating. When nitric oxide availability falls, one of the vessel lining's natural signals for keeping platelet activity under control is reduced. [2]

3. Vessels Stay a Little Tighter, Even at Rest

Your blood vessels are never fully relaxed or fully tight. The lining releases a steady amount of nitric oxide that helps regulate normal resting vascular tone. In healthy adults, researchers found that blocking nitric oxide production reduced resting forearm blood flow by about 50%. This shows how continuously produced nitric oxide helps keep blood vessels open enough to maintain normal blood flow at rest. [3]

4. Vessels Open Up Less When You Need More Blood

When blood flow increases, the movement of blood against the vessel wall sends a signal for the artery to widen. Nitric oxide is a major part of that response. In healthy adults, researchers found that blocking nitric oxide production abolished normal flow-mediated dilation in the radial artery and caused the artery to constrict instead. This shows how important nitric oxide is for helping arteries widen when blood flow increases. [4]

5. The Muscle in the Vessel Wall Can Thicken

Nitric oxide also helps regulate the growth of smooth muscle cells inside the vessel wall. In mice unable to produce normal endothelial nitric oxide, researchers observed increased arterial wall thickness along with increased cell growth after a vascular remodeling stimulus. The findings showed that nitric oxide acts as an important brake on excessive vascular smooth muscle growth. [5]

6. Arteries Lose Some of Their Stretch

Healthy large arteries stretch a little with every heartbeat, then spring back. That stretch helps soften the force of each pump before it reaches smaller vessels. In an animal study, blocking nitric oxide production increased arterial stiffness even without a significant change in systemic blood pressure. The findings suggest that nitric oxide itself helps regulate how flexible large arteries remain. [6]

7. Your Body Builds Fewer New Small Blood Vessels

Your body can grow new tiny blood vessels to reach areas that need more blood. Nitric oxide is one of the signals involved in that process. In mice unable to produce endothelial nitric oxide normally, new blood vessel growth after reduced blood flow to the leg was significantly impaired compared with normal mice. This shows that endothelial nitric oxide plays an important role in the body's ability to form new blood vessels when tissue needs additional circulation. [7]

Conclusion

Each of these seven changes starts in the same place: the thin lining inside your blood vessels. When that lining makes less nitric oxide, the effects can spread outward, from the blood cells moving past, to the muscle in the vessel wall, to how well your arteries stretch and open when your body needs more blood.

Most of these shifts happen slowly and quietly, without anything you would necessarily feel. They can build on one another over time, which is why researchers pay such close attention to how well the blood vessel lining is working.

Knowing what nitric oxide does, and what changes when there is less of it, gives you a clearer picture of what is happening inside your blood vessels every day.