Electron-cytochemical localization of succinic semialdehyde dehydrogenase activity in Purkinje neurons and hepatocytes of the rat.

A method is presented for the ultrastructural demonstration of succinate semialdehyde dehydrogenase (SSADH) activity in cerebellar Purkinje neurons and liver hepatocytes; SSADH is an enzyme involved in the degradation of gamma-aminobutyric acid (GABA). Incubation media originally used for light microscopy were considered. Reaction products were mainly detected when fresh tissue was used. In Purkinje cells, grains ascribable to SSADH activity were localized on the mitochondria (especially on the outer membrane); some extramitochondrial formazan deposits were also found. After brief fixation by immersion or perfusion, only a few formazan granules were detected in the cytoplasm. A similar distribution pattern was observed in hepatocytes, in which extramitochondrial grains and grains on the nuclear membrane were frequent. The actual existence and the possible meaning of extramitochondrial SSADH activity is critically discussed on the basis of the data in the literature.