Abstract

The enzyme lactate dehydrogenase (LDH) is found in metabolically active cells, especially heart, liver, brain, skeletal muscles, kidneys, and blood. During metabolism, enzymes are released into the bloodstream at a constant rate. Serum LDH can be subdivided into five primary isoenzymes, LDH₁ through LDH_5, by electrophoresis.²

When tissues are damaged, serum LDH rises due to cellular leakage, and the resultant isoenzyme patterns reflect isoenzymes found in the affected tissue.^2-6,8

Serum LDH isoenzyme activity was analyzed in cetaceans. Different clinical conditions such as intramuscular injection, azole therapy, and apparent trauma produced distinctly different LDH isoenzyme profiles in cetaceans. A fourth distinctive pattern was occasionally observed in clinically normal animals with elevations in transaminase and LDH activities. LDH isoenzyme activity patterns were not affected by mild or moderate hemolysis, refrigeration over 24 hours or freezing for 24 hours with subsequent thawing. However, severe hemolysis produced artifactual changes similar to those observed in individuals who received injections, but of a lesser magnitude. LDH isoenzyme activity patterns may provide useful corroboration of other clinical findings when diagnostic modalities are limited, especially to differentiate non-specific enzyme elevation from non-pathologic elevations in serum enzyme concentrations due to intramuscular injections or azole therapy.

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References

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