Atrial Natriuretic
Peptide

The Discovery

The Unexpected Discovery

In 1981, a Canadian physiologist named Adolfo de Bold made a discovery that shocked the medical w...

In 1981, a Canadian physiologist named Adolfo de Bold made a discovery that shocked the medical world. He took tissue from the atria — the upper chambers of a rat's heart — ground it up, and injected the extract into other rats. Within minutes, the rats produced a massive amount of urine. Their blood pressure dropped. Something in heart tissue was controlling the kidneys and blood vessels. De Bold had proven something revolutionary: the heart wasn't just a pump. It was also a hormone-producing gland. Scientists had overlooked this for centuries because they assumed the heart's only job was to push blood around the body.

The Breakthrough

The Scientific Explosion

De Bold's discovery triggered a worldwide race to identify the mystery hormone.

De Bold's discovery triggered a worldwide race to identify the mystery hormone. Within three years, multiple teams isolated it. They called it atrial natriuretic peptide, or ANP, because it came from the atria and caused natriuresis — the release of sodium in urine. ANP was 28 amino acids long with a distinctive ring shape formed by a chemical bridge. Scientists quickly found that the heart released ANP whenever blood volume increased too much. It was nature's pressure release valve: when your blood pressure got too high, your heart released ANP to make your kidneys flush out water and salt, bringing pressure back down.

The Trials

From Laboratory to Patients

Clinical trials in the late 1980s and early 1990s tested synthetic ANP in patients with heart fai...

Clinical trials in the late 1980s and early 1990s tested synthetic ANP in patients with heart failure and high blood pressure. The results were mixed. ANP worked — it lowered blood pressure, reduced fluid overload, and helped the kidneys function better. But it had a problem: it broke down in the bloodstream within minutes. Patients needed continuous IV infusions. Several pharmaceutical companies tried to create longer-lasting versions. Nesiritide, a synthetic form of the related peptide BNP, eventually won FDA approval in 2001 for acute heart failure. But the quest for a stable, long-lasting ANP pill continues today.

The Crisis

The Biomarker Revolution

While ANP itself struggled as a drug, it became one of the most valuable diagnostic tools in card...

While ANP itself struggled as a drug, it became one of the most valuable diagnostic tools in cardiology. Doctors discovered that measuring BNP and its fragment NT-proBNP in blood could tell them whether a patient was in heart failure. Higher levels meant worse heart failure. The blood test was cheap, fast, and remarkably accurate. Emergency rooms around the world adopted it. When a patient came in short of breath, a quick BNP test could distinguish heart failure from lung disease within minutes. This single test changed emergency medicine forever, saving time, money, and lives by enabling faster, more accurate diagnosis.

The Legacy

Today and Tomorrow

Today, natriuretic peptide blood tests are performed hundreds of millions of times each year worl...

Today, natriuretic peptide blood tests are performed hundreds of millions of times each year worldwide. They guide treatment decisions for millions of heart failure patients. Researchers have also discovered that the natriuretic peptide system does far more than control blood pressure — it affects fat metabolism, bone growth, and even brain function. New drugs called neprilysin inhibitors (like sacubitril, combined with valsartan in the drug Entresto) work by preventing the body from breaking down ANP too quickly. This approach has become one of the most important advances in heart failure treatment in decades. De Bold's curious experiment with rat heart tissue launched an entire field of cardiovascular medicine.