#Albumin

#Albumin synthesis

Normal plasma concentration in healthy individuals

• 40–50 g/L

Site and rate of synthesis

• Synthesised exclusively by the liver
• Production rate ≈ 10 g/day in adults

Factors increasing albumin synthesis

• Increased substrate availability
  • Increased protein intake
  • Increased caloric intake
• Hormonal influences
  • Growth hormone
  • Corticosteroids
  • Insulin
• Physiological signals
  • Decreased plasma oncotic pressure (stimulates synthesis)

Factors decreasing albumin synthesis

• Malnutrition
• Increased plasma oncotic pressure
• Critical illness
  • Sepsis
  • Trauma
• Liver disease
  • Reduced hepatocyte synthetic capacity

#Role of Albumin

Anti-inflammatory

• Binds pro-inflammatory cytokines, inactivating them
• Attenuates the systemic inflammatory response

Antioxidant

• Contains a thiol group that scavenges reactive oxygen species and free radicals, inactivating them
• Responsible for approximately 70% of the body's antioxidant capacity

Maintenance of oncotic pressure

• Capillary membranes are largely impermeable to proteins
• Albumin generates ~25 mmHg of plasma oncotic pressure
• Maintains intravascular volume and limits interstitial oedema

Endothelial protection

• Preserves the endothelial glycocalyx
• Reduces capillary leak

Binding and transport functions

• Binds and transports endogenous and exogenous substances, including:
  • Bilirubin
  • Hormones
  • Fatty acids
  • Drugs
• Facilitates transport across cell membranes
• Influences drug distribution, metabolism, and clearance

Acid–base buffering

• Amphoteric protein which can donate or accept hydrogen ions
• Contributes to plasma buffering capacity

Protein reserve

• Constitutes ~50% of total plasma protein
• Acts as a marker of nutritional status

Anticoagulant properties

• Enhances antithrombin III activity
• Contributes to endogenous anticoagulation