Removes an H from its preferred substrate. There are 5 isoenzymes: LLLL, LLLH, LLHH, LHHH, and HHHH – LD 5, 4, 3, 2, 1.
- Reaction catalyzed in the laboratory:
- Wacker Reaction (most common)
- Lacic Acid + NAD+ -----------> Pyruvate + NADH
- Wroblewski Reaction (Vitros-Preferred)
- Pyruvate + NADH --------------------> Lactic Acid + NAD+
- Tissue(s) of enzyme abundance:
- All cells of all tissues have this enzyme.
LD isoenzyme electrophoresis can isolate isoenzymes.
Typically: LD-2 > LD-1 > LD-3 > LD-5 > LD-4
- LD-1 and LD-2:
- RBCs and WBCs (and bone marrow).
- Heart (LD-1 > LD-2 – LD Flip)
LD-3: Lung Tissue. Seen in Pulmonary Embolisms with Pulmonary Infarcts.
- LD-4 and LD-5:
- Smooth and Skeletal Muscle (Trauma & MD)
- Liver (Hepatic Disease)
- Kidney (Renal Necrosis and Renal Infarcts)
- Elevations >3x normal range
- RBCs and WBCs
- Skeletal Muscle and Smooth Muscle.
Liver or other tissues (pancreas, bone, kidney, etc) usually won’t double normal range.
- Special Specimen handling precautions:
- Serum or heparinized plasma may be used on most instruments.
Hemolyzed RBCs will release tons of LD. Hemolysis is completely unacceptable.
Should not be frozen. Will give slightly lower values.