Heparin, 1916 – Preventing Blood Clotting

Blood clotting is vital, but uncontrolled clotting can be fatal. This is where anticoagulants such as heparin come in. This article examines its medical importance, history and varied uses.

Heparin: Controlling Blood Clotting

Heparin is a powerful anticoagulant—a medicine preventing blood clotting. It is important during open-heart surgery, organ transplantation, kidney dialysis and blood transfusion, and sometimes coats medical devices contacting blood. It also helps treat the potentially fatal obstruction of blood flow to the lungs associated with thrombosis (formation of a blood clot inside a vessel).

Heparin’s Source: From Nature to the Laboratory

Heparin can be obtained from pig intestines or cow lungs. It also occurs across the animal kingdom, even in lobsters and mussels, which lack blood-clotting systems, suggesting other biological roles.

Unsustainable extraction from animal tissues and potential contamination risks have driven research into alternative production methods. This is where biotechnology becomes important.

Microbial Production: Effective and Safe

Biotechnological methods generally use microorganisms or cell cultures to produce heparin. Genetically modified bacteria or yeast cells, for example, can supply the enzymes and building blocks, making production faster, more effective and safer.

Enzyme-Catalysed Synthesis: Precise and Customisable

Another approach combines the specific carbohydrate building blocks of heparin using particular enzymes. This enables much more precise control over the molecule’s structure.

How Heparin Works

Heparin is a carbohydrate polymer naturally produced by certain white blood cells (a long molecule made of repeating structural units). It does not dissolve existing clots but prevents their growth and formation of new ones. One route of action involves:

• Binding to antithrombin III to inactivate a small protein; and
• Inhibiting thrombin, a clotting protein in the circulation.

Heparin’s History: From Discovery to Today

Heparin is among the oldest medicines still widely used. Research began in 1916, when American researchers Jay McLean and William Howell investigated anticoagulant compounds in dog liver. Between 1933 and 1936, Canadian researcher Charles Best and colleagues developed a method of producing heparin safe for humans.

Its uses now range from topical gels for sports injuries (reducing inflammation by blocking histamine) to catheter (thin plastic tube) coatings and heart–lung machine components. Other current anticoagulants include coumarins, which block vitamin K function (for example, warfarin, also used as a rodenticide). 

A famous warfarin user was US President Dwight Eisenhower following his heart attack in 1955. Some historians also suggest that high-dose warfarin was used to kill Soviet leader Joseph Stalin in 1953.

Low-Molecular-Weight Heparins

Low-molecular-weight heparins (LMWHs) are smaller than standard heparin and provide more predictable anticoagulation. Clexane (enoxaparin) is a well-known example, often used for deep vein thrombosis, pulmonary embolism and acute coronary syndromes, and to prevent clots before and after surgery. These broad uses make LMWHs common anticoagulant options.

Historical figures mentioned: William Henry Howell (1860–1945), Jay McLean (1890–1957), Charles Herbert Best (1899–1978)

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