In horses, the blood chemistry tests most commonly used to evaluate liver function are:

• A. Alanine transaminase and aspartate aminotransferase
• B. Electrolytes and blood urea nitrogen
• C. Gamma-glutamyl transferase and sorbitol dehydrogenase
• D. Amylase and lipase

Answer: (C)

Evaluating liver function in horses relies on enzymes that signal different aspects of hepatobiliary health. Gamma-glutamyl transferase (GGT) is concentrated in the biliary tract and rises with cholestasis and biliary injury, making it a sensitive indicator of biliary disease in horses. Sorbitol dehydrogenase (SDH) is a hepatocellular enzyme with high liver specificity in this species and a short half-life, so it increases rapidly after acute liver cell injury and reflects acute damage. Together, these two enzymes cover the main patterns of liver injury clinicians monitor. Other options are less reliable for hepatic assessment in horses: alanine aminotransferase and aspartate aminotransferase can be influenced by muscle and are not as liver-specific in horses; electrolytes and blood urea nitrogen measure kidney function and hydration status, not liver integrity; amylase and lipase indicate pancreatic activity rather than liver.