LABORATORY EVALUATION OF MUSCLE DISEASE IN DOMESTIC ANIMALS

32 LABORATORY EVALUATION OF MUSCLE DISEASE IN DOMESTIC ANIMALS



1 What serum enzyme tests can be used to evaluate muscle degeneration or necrosis?


Creatine kinase (CK), aspartate transaminase (AST), and lactate dehydrogenase (LDH) have been used to evaluate muscle disorders in dogs, cats, ruminants, and horses. Alanine transaminase (ALT) has been used as a muscle specific enzyme in ruminant and horses because very little is present in liver. Serum activities increase with degenerative and necrotic lesions but do not increase with muscle atrophy or neoplasia.



2 Which of the muscle enzymes is the most specific for detection of muscle disease?


CK is highly specific for muscle injury. Although CK is present in low amounts in intestine, uterus, kidney, and urinary bladder, a substantial increase in serum CK activity is almost always an indication of skeletal or cardiac muscle degeneration or necrosis. CK activity increases within a few hours of onset of muscle necrosis. CK has a short half-life in plasma. As a result, CK activity returns to normal within 24 to 48 hours after cessation of muscle injury. Therefore a persistent increase in serum CK activity can be interpreted as continued muscle injury.



3 Which of the muscle enzymes is the most sensitive test of muscle injury?


CK is a very sensitive indicator of muscle injury. Even minor muscle injury, such as intramuscular injection, minor trauma associated with transportation of large animals, and strenuous exercise, will result in increased serum CK activity. AST activity increases more slowly in plasma. LDH activity increases rapidly, but the magnitude of increase is less than that of CK.



4 Does determination of creatine kinase (CK) and aspartate transaminase (AST) provide any additional information beyond determination of CK alone?


AST is present in most cells, but increased activity in serum is usually associated with liver or muscle disease. AST is also present in erythrocytes, so hemolysis may increase serum activity. The combination of CK and AST can be used to pinpoint the cause of the increase in AST activity. If both are increased, the disease process is probably related to muscle injury, whereas if AST activity is increased and CK activity is normal, the disease process is probably located in the liver. However, AST decreases more slowly after cessation of muscle injury. Therefore, previous muscle injury cannot be ruled out when increased AST activity and normal CK activity is observed.



5 Are creatine kinase (CK) isoenzymes useful in evaluating increased serum CK activity?


Two subunits of CK are present: B for brain and M for muscle. Each molecule of CK consists of two of these subunits. The BB isoenzyme (CK1) is found in the brain, the MB isoenzyme (CK2) primarily in cardiac muscle, and the MM isoenzyme (CK3) in skeletal and cardiac muscle. CK1 activity may increase in cerebrospinal fluid with brain injury but does not increase in plasma. Skeletal muscle injury primarily results in an increase in CK3, whereas cardiac muscle injury results in an increase in CK2 and CK3.

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  4. METABOLIC ACID-BASE ABNORMALITIES

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Aug 26, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on LABORATORY EVALUATION OF MUSCLE DISEASE IN DOMESTIC ANIMALS

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