Cytoglobin, also named as Histoglobin, HGb, STAP and CYGB, belongs to the globin family. Cytoglobin may have a protective function during conditions of oxidative stress. It may be involved in intracellular oxygen storage or transfer. It serves as a defensive mechanism against oxidative stress both in vitro and in vivo.(PMID:21224051) Cytoglobin is a ubiquitously expressed hexacoordinate hemoglobin that may facilitate diffusion of oxygen through tissues. The protein, with calculated MW of 21 kd, runs as a 29kd one in canine retina, kidney, liver, lung, and heart. It may be caused by posttranslational modification of the protein. Various immuno-staining patterns were reported including nuclear, cytoplasm and extracellular location.