Effects of detergents on Ca(2+)-activated neural proteinase activity (calpain) in neural and non-neural tissue: a comparative study

The localization of mcalpain in myelin: immunocytochemical evidence in different areas of rat brain and nerves

A major part of brain mcalpain activity has been found associated with myelin, but its presence in the myelin sheath has not been clearly demonstrated by microscopic (morphological) means. Using myelin mcalpain antisera the localization of mcalpain has been investigated in tissue of rat CNS and PNS by immunohistochemical methods. These experiments also have been carried out by double labeling studies using antibodies to myelin basic protein (MBP) and neurofilament protein (NFP). Our results indicate calpain/MBP immunoreactivity in the myelin sheath surrounding the axon while NFP antibody stained inside the axon in spinal cord; pons, cerebellum, trigeminal nerve, and sciatic nerve. Patches of light immunoreactivity of calpain were also seen in the axonal cytoplasm. The calpain immunostaining of myelin was similar to that of MBP staining indicating the presence of calpain in myelin. This finding supports the view that calpain is a constituent of myelin, may be involved in the normal turnover of myelin proteins. In pathological situations such as in demyelinating and other brain degenerative diseases, myelin may be autodigestive.