In healthy people, a substance in blood vessels called nitric oxide helps keep blood pressure and vessel tightness in check. When scientists blocked this substance, blood vessels tightened up and blood pressure went up, showing how important it is for keeping things normal.

When the lining of blood vessels isn't working right and makes less of a substance that keeps vessels open, it can raise blood pressure — even if the heart's pumping and blood amount stay the same.

In healthy people, a molecule called nitric oxide helps keep blood vessels in the lungs open and relaxed when oxygen levels are normal. When scientists blocked its production, the lung blood vessels became more resistant to blood flow, even though overall pressure didn’t change.

When doctors blocked a chemical called nitric oxide in healthy people, their hearts pumped less blood with each beat and overall, showing that this chemical helps keep the heart working normally when we're just resting.

A molecule called nitric oxide helps your blood vessels relax, your heart pump better, and your cells make energy properly — when this system goes wrong, it can lead to high blood pressure and heart problems.

When healthy adults get a certain drug in their leg artery, blood flow drops by up to 45%, and insulin makes this drop even bigger — showing that insulin helps control blood flow in muscles by affecting nitric oxide.