Pimonidazole, the exogenous hypoxia marker, is a 2-nitroimidazole compound, which forms covalent bonds with cellular macromolecules at oxygen levels below 1.3%.
Detection: Hypoxic cells were recognized by immunohistochemical detection of pimonidazole using a mouse monoclonal antibody. Cell proliferation was detected with a commercially available monoclonal antibody for proliferating cell nuclear antigen (PCNA). Assessment of hypoxia and cell proliferation was made qualitatively with light microscopy and quantitatively using point counting and image analysis software methods.
The pimonidazole-protein adducts were then detected by immunofluorescence
Cells (90% confluent) are treated with pimonidazole hydrochloride (10-100 μM), diluted in complete media or PBS, and placed in hypoxia or normoxia for 2-4 hours.
Then, cells are washed 4 times in HBSS, fixed for 10 min with 10% neutral buffered formalin at room temperature, washed 3 times with tris buffered saline, and mounted with Prolong Gold with DAPI mounting media.
To monitor the intrinsic hypoxic signal, the tissue is removed and the embryos incubated with 400 µM pimonidazole for 2 h before fixation. Immunostaining is performed using antibodies against pimonidazole-protein adducts (Hypoxyprobe).