Lactatedehydrogenase (LDH) oxidizes lactic acid into pyruvate. This enzyme is present in cells capable of glycolysis and is released when the cell becomes damaged or dies. There are five isoforms of LDH, with LDH-5 found in different tissues. The liver and skeletal muscle exhibit high LDH activity. Normal red blood cells contain about 100 times more LDH than serum. LDH-1 is H-type (heart-type), associated with aerobic metabolism, while LDH-5 is M-type (muscle-type), linked to anaerobic metabolism.

The Lactate Dehydrogenase (LDH) Staining Kit (Tetrazole Method) utilizes lactate as the substrate. Under LDH catalysis, nitroblue tetrazole (NBT) acts as the hydrogen acceptor. After accepting hydrogen, NBT is reduced to methylene blue, producing a blue-purple coloration that indicates LDH activity. However, this method cannot distinguish between different types of LDH. The LDH incubation solution contains a specific intermediate hydrogen carrier, which enhances localization accuracy and staining clarity.