Immunocytochemistry of the taurine biosynthesis enzyme, cysteine sulfinate decarboxylase, in the cerebellum: evidence for a glial localization.

Immunocytochemistry of cysteine sulfinate decarboxylase was developed in the cerebellum with an antiserum that we have recently produced using as immunogen a homogeneous fraction purified about 2000-fold from liver. In the rat, this antiserum immunoprecipitated the enzymatic activity from brain, labeled one band (molecular weight = 51,000) on immunoblots of an enriched fraction from brain but none with a brain crude extract and thus appeared to be specific. In the cerebellum numerous immunolabeled cells were found in the white matter that were typically arranged in rows like oligodendrocytes. A few immunolabeled cells were scattered in the granular layer. Around the Purkinje cells numerous small satellite cells were immunostained that sent faintly labeled radial fibers through the molecular layer. These cells were thus identified as Golgi epithelial cells with their Bergmann fibers. Purkinje cells were not labeled either at the cell body or at the nerve ending levels. In the molecular layer no cells were found consistently and convincingly immunolabeled that could correspond to the stellate cells. No immunopositive punctae typical of the interneuron nerve endings were ever observed. A significant cysteine sulfinate decarboxylase activity was also measured in glial cell fractions enriched in oligodendrocytes and astrocytes respectively. The glial localization of taurine biosynthesis enzyme in the cerebellum does not support the hypothesis that it could be involved in neurotransmission, but rather suggests that taurine is manufactured by glial cells and accordingly may play a physiological role in relation to glial function.