Lactate dehydrogenase isoenzymes in blood and cerebrospinal fluid from healthy beagles.

Serum and CSF lactate dehydrogenase (LDH) activity and LDH isoenzyme profile, as well as total protein, were measured in samples obtained from 26 healthy Beagles. The LDH activity in serum was approximately 10 times that in the CSF. The CSF LDH isoenzyme profile was a mirror image of the serum LDH isoenzyme profile. Age was negatively correlated (ie, as age increased, the activity decreased) with LDH3 in CSF and LDH5 in serum and was positively correlated with LDH1 in serum. Seemingly, simultaneous measurement of serum and CSF LDH activity and LDH isoenzyme profile can aid in establishing status of the blood-brain barrier, whether brain damage exists and whether other organ systems are involved.