IMMUNOCHEMICAL AND IMMUNOHISTOCHEMICAL LOCALIZATION OF BCL-X PROTEIN IN THE RAT CENTRAL-NERVOUS-SYSTEM

To explore the role of bcl-x in the regulation of cell death in the ne rvous system, we produced monoclonal antibodies against rat Bcl-x(L) p rotein, the major product of the rat bcl-x gene that inhibits apoptosi s, and defined its distribution in rat neural tissues by immunochemica l and immunohistochemical means. Western blotting of tissue homogenate s identified the Bcl-x protein as two bands with molecular weights of about 29 and 31 kDa. The level of Bcl-x expression in the nervous syst em was high, being comparable to that in the hematolymphoid system, an d higher in the fetal than in the adult brain. Subcellular fractionati on studies localized Bcl-x to various subcellular compartments. In tis sue culture, Bcl-x was produced by all the cell types examined, includ ing neurons, astrocytes, oligodendrocytes and microglial cells. Immuno histochemistry revealed that Bcl-x immunoreactivity was more intense i n the gray than in the white matter. In the fetal cerebral cortex, lab eling was mostly confined to the neuronal perikarya, whereas in the mo re mature brain, the neuropil of the gray matter, as well as the glial cells in the white matter, was also stained.