IMMUNOCYTOCHEMICAL LOCALIZATION OF CYSTEINE SULFINATE DECARBOXYLASE IN ASTROCYTES IN THE CEREBELLUM AND HIPPOCAMPUS - A QUANTITATIVE DOUBLEIMMUNOFLUORESCENCE STUDY WITH GLIAL FIBRILLARY ACIDIC PROTEIN AND S-100 PROTEIN

Immunocytochemistry of cysteine sulfinate decarboxylase was performed with a new rabbit antiserum that we have recently produced and charact erized using as antigen an 11,000-fold purified fraction isolated from rat liver. This antiserum precipitated cysteine sulfinate decarboxyla se enzymatic activity, labeled one band (mol, wt 51,000) on immunoblot s of crude tissue extracts and did not stain any cells in peripheral t issues devoid of cysteine sulfinate decarboxylase. According to these criteria, this antiserum appeared to be specific for cysteine sulfinat e decarboxylase. Numerous cells were immunolabeled in the cerebellum a nd the hippocampus. Most notable was the labeling of the small cells s urrounding the Purkinje cells and sending radial fibers up to the pial surface of the cerebellar cortex or the staining of small star-shaped cells with thin immunolabeled processes abutting on blood vessels. Id entified nerve cells such as the Purkinje cells and granule cells in t he cerebellum or the pyramidal and granule cells in the hippocampus we re devoid of any immunoreactivity. Simultaneous double immunofluoresce nce was carried out using anti-glial fibrillary acidic protein or anti -S-100 monoclonal antibodies. Cysteine sulfinate decarboxylase as well as glial fibrillary acidic protein- or S-100-immunopositive cells wer e plotted independently for the same section. Quantitative analysis of the maps indicated that the overwhelming majority of cysteine sulfina te decarboxylase-immunolabeled cells were positive for the established astrocytes markers, glial fibrillary acidic protein or S-100. Between 82 and 98% of cysteine sulfinate decarboxylase-immunolabeled cells we re also glial fibrillary acidic protein-positive, depending upon the l ayer. Cysteine sulfinate decarboxylase immunostaining was localized wi thin the cytoplasm, while that of glial fibrillary acidic protein was linked to the cytoskeleton. Since both labels could not be fully super posed, some double immunolabeled cells may have escaped our analysis. More than 94% up to 99% of cysteine sulfinate decarboxylase-immunolabe led cells were simultaneously S-100-immunopositive. Our quantitative d ata establish that cysteine sulfinate decarboxylase is strictly locali zed in astrocytes in the cerebellum and in the hippocampus. This findi ng suggest that taurine is synthesized by astrocytes in the brain and accordingly may play a role in relation to glial function, possibly wi thin the framework of glial-neuronal interactions. Copyright (C) 1996 IBRO.