Plasma membranes from neuronal perikarya (N), protoplasmic astrocytes (A) and oligodendrocyies (O) of rat brains were analysed with respect to their protein and glycoprotein contents and specificities. SDS-polyacrylamide gel electrophoresis revealed a total number of 23, 17, and 17 major proteins in N, A, and O respectively. Periodate-Schiff''s staining showed that approximately 40-60% of these proteins were glycoproteins. The reactivity of these glycoproteins to Con A and WGA was also studied. Selective iodination of whole cells followed by electrophoresis and autoradiography indicated that of the major proteins, only 25% of neuronal and 60% of astroglial and oligodendroglial membrane proteins were exposed outside the cell surface. The overall results suggest that membrane proteins of each of the three cell types studied here have characteristically different internal and external markers differing in size, glycoprotein content, and reactivity of the glycoproteins to lectins
