Phosphotungstic acid-haematoxylin stain
It stains some tissue in contrasting colors in a way similar to haematoxylin and eosin stain, as phosphotungstic acid binds to tissue proteins. It is used to show gliosis in the central nervous system, tumours of skeletal muscles, and fibrin deposits in lesions. Muscle is stained blue-black to dark brown, connective tissue is pale orange-pink to brownish red, fibrin and neuroglia stain deep blue, coarse elastic fibers show as purple, and bone and cartilage obtain yellowish to brownish red color.
There is much more phosphotungstic acid in the solution than hematein. The phosphotungstic acid binds all of the available hematein to form a blue lake pigment. This lake stains the muscle cross striations, fibrin, nuclei, and other tissue elements blue. The rest of the phosphotungstic acid stains the red-brown components, such as collagen.
Staining Procedural Notes
Zenker fixative is preferred, although formalin fixed tissue can be used. If this is the case, the tissue should be mordanted in Zenkers solution before staining.Most texts recommend mordanting in Zenker fixative overnight at room temperature, but it can be done for 3.5 hours in a 56 to 60 degrees Celsius oven.
PTAH solution, Gram Iodine, 5% sodium thiosulfate, 0.25% Potassium Permanganate, and 5% Oxalic Acid solution are needed.
After staining, slides should be dehydrated quickly because the red-brown components lose their color when exposed to water or alcohol.