Lactic dehydrogenase isoenzymes in equine infectious anemia.

The study investigates the potential for lactic dehydrogenase isoenzymes to be a useful diagnostic tool for equine infectious anemia, a disease that shows similarities to infectious mononucleosis in humans.

Background of the Study

• This research was motivated by the well-established diagnostic and clinical value of lactic dehydrogenase (LDH) isoenzymes in humans. Specifically, their capacity for more organ-specific and potentially more sensitive detection of disease than total enzyme activity metrics.
• The researchers were considering potential laboratory tests that could help diagnose equine infectious anemia (EIA), and it seemed LDH isoenzymes might be the most promising tool.
• Jubb and Kennedy notably influenced this study with their descriptions of hepatic, cardiac, and renal changes that are associated with EIA. The disease resembles infectious mononucleosis in humans both in clinicalpresentation and laboratory results.

LDH Isoenzymes and Disease

• LDH isoenzymes often show up in different ways depending on the conditions of the disease. Cawley highlighted that LDH3 increases with uncomplicated cases of infectious mononucleosis. If there is liver involvement, LDH5 appears and, for situations where hemolysis is a factor, LDH1 and LDH2 become pronounced.
• Clearly, there is a link between specific LDH isoenzymes and certain physiological changes associated with diseases. Therefore, understanding how these isoenzymes appear and behave provides valuable diagnostic tools for physicians.

LDH Isoenzymes in Horses

• Gerber’s work on LDH isoenzymes in horses influenced this study. Gerber’s significant discovery was of six isoenzymes in the liver extract of horses. In the serum of healthy horses, three to four isoenzymes were found—unusually high numbers compared to other species.
• The more cathodic fractions (LDH4 and LDH5) did not show up in a significant concentration in the serum of healthy horses. However, these isoenzymes are known to appear under specific conditions of diseases, so their absence in healthy individuals makes sense.