Creatine kinase and its isoenzymes in the serum and cerebrospinal fluid of healthy canines.

BACKGROUND: Creatine kinase (CK) exists as three isoenzymes (CK-MM, CK-MB, and CK-BB) that are predominantly expressed in specific tissues and can be detected in both the serum and cerebrospinal fluid (CSF). CSF CK has been relatively unstudied in veterinary medicine, although studies in human medicine have demonstrated that changes in total CSF CK activity can indicate neurologic abnormalities. OBJECTIVES: The purpose of this study was to establish reference intervals for CK and its three major isoenzymes in the serum and CSF of clinically healthy dogs. By establishing a definitive reference interval for this enzyme in healthy canines, the diagnostic use and possible significance of CK in clinical disease can be studied. METHODS: Serum and/or CSF were collected from healthy dogs. Total CK activity was measured spectrophotometrically, and isoenzyme distributions were determined using the QuickGel CK Vis Isoenzyme Kit and a densitometric scanner. Total CK and CK isoenzyme activities were determined within 8 h of collection. RESULTS: The median serum total CK in healthy canines was 159.0 U/L (range: 53.0-539.0 U/L), while the median CSF total CK was 3.7 U/L (range: 2.0-84.0 U/L). CK-BB and CK-MM were approximately equal in the serum, while CK-MM was the predominant isoenzyme in the CSF. CONCLUSIONS: Knowledge of the normal distribution and concentration of CK in canine serum and CSF will set the foundation for future studies of canine CK as a potentially clinically useful biomarker.

Reference intervals for the activity of lactate dehydrogenase and its isoenzymes in the serum and cerebrospinal fluid of healthy canines.

BACKGROUND: Lactate dehydrogenase (LD) exists as 5 isoenzymes (LD-1 through LD-5) that are expressed throughout the body and can be detected in both serum and cerebrospinal fluid (CSF). LD and its isoenzymes have been relatively unstudied in veterinary medicine, although studies in human medicine have demonstrated that changes in total LD activity and atypical isoenzyme patterns can indicate disease processes, including neurologic abnormalities. OBJECTIVES: The purpose of this study was to establish RIs for LD and its isoenzymes in the serum and CSF of clinically healthy dogs. By establishing a definitive RI for this enzyme in healthy canines, further study of the clinical and diagnostic usefulness of LD can be undertaken. METHODS: Serum and atlantoaxial CSF were collected from clinically healthy dogs. Total LD activity was measured spectrophotometrically immediately after collection. Isoenzyme distributions were also determined within 8 hours of collection using the QuickGel LD Isoenzyme technique and a densitometric scanner. RESULTS: The median serum total LD in healthy canines was 69.0 U/L (n = 41; range: 21.0-217.0 U/L), while the median CSF total LD was 10.0 U/L (n = 40; range: 6.0-19.3 U/L). LD-5 is the predominant isoenzyme in canine serum (n = 40), contributing over half of the total enzyme activity. Conversely, in canine CSF (n = 42), LD-1 is the predominant isoenzyme, followed by LD-2 and LD-3. CONCLUSIONS: Knowledge of the distribution and concentration of LD in the serum and CSF of healthy dogs will set the foundation for future studies of canine LD as a potentially clinically useful biomarker.

Determination of optimal storage temperature and duration for analysis of total and isoenzyme lactate dehydrogenase activities in canine serum and cerebrospinal fluid.

BACKGROUND: Lactate dehydrogenase (LDH) exists as 5 isoenzymes in both serum and cerebrospinal fluid (CSF). Human studies have demonstrated that changes in LDH activity can be correlated with a particular disease. OBJECTIVES: Conflicting reports regarding the stability of LDH made it necessary to determine storage conditions before further study of the diagnostic power of this enzyme's activity can be pursued in dogs. The purpose of this study was to optimize measurement of LDH activity and analysis of its isoenzyme profile in canine serum and CSF through proper storage. METHODS: Serum and CSF were collected from 5 healthy dogs. Samples were stored at 22°C, 4°C, or -20°C for up to 2 months. Total LDH activity was measured spectrophotometrically. Isoenzyme profiles were determined using the QuickGel LDH Isoenzyme technique and densitometric scanning. Retention of > 70% LDH activity in stored samples was considered clinically acceptable. RESULTS: Serum and CSF stored at -20°C retained > 85% of the total LDH activity for 4 weeks, although CSF total LDH activity degraded by > 10% within 24 hours of storage. All serum LDH isoenzymes retained > 85% activity for up to 4 weeks at -20°C. CSF LDH isoenzyme activity degraded rapidly, therefore CSF LDH should be evaluated within 72 hours to assure > 75% of LDH isoenzyme activity. CONCLUSIONS: Proper storage at -20°C can optimize detection of total LDH activity and the LDH isoenzyme profile in canine serum and CSF. This information is important for evaluating the potential usefulness of LDH in veterinary medicine.