Question

Which of the following enzyme is considered to be liver specific in the case of dogs and cats, but not clinically significant in horses and ruminants?

• A. Aspartate transaminase
• B. Alanine transaminase
• C. Alkaline phosphatase
• D. Sorbitol dehydrogenase

Hint:

For small animal biochemistry (dogs/cats), use ALT as the primary liver leakage marker. For large animal biochemistry (horses/ruminants), use SDH or GLDH.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Diagnostic enzymology relies on measuring serum enzyme activities that rise following cellular injury.
The clinical utility of a leakage enzyme depends on its tissue distribution, which can vary significantly among different animal species.

Step 2: Detailed Explanation:
Let us compare the tissue distribution of the transaminases:
- Alanine Transaminase (ALT): In dogs, cats, primates, and humans, ALT is concentrated within the cytoplasm of hepatocytes.
Consequently, an increase in serum ALT activity is highly specific for hepatocellular leakage or necrosis in these species.
However, in horses, pigs, and ruminants (cattle, sheep, goats), hepatocytes contain very little ALT activity.
In these large animals, normal liver turnover or injury does not release enough ALT to cause a diagnostic rise in serum, making it clinically insignificant.
Instead, other enzymes like Sorbitol Dehydrogenase (SDH) or Glutamate Dehydrogenase (GLDH) are used as liver-specific markers in large animals.
- Aspartate Transaminase (AST) is not liver-specific in any of these species, as it is also present in skeletal and cardiac muscle.

Step 3: Final Answer:
Alanine transaminase (ALT) is liver-specific in dogs and cats, but lacks clinical significance in horses and ruminants.