DETERMINATION OF BRAIN‐SPECIFIC ANTIGENS IN SHORT TERM CULTIVATED RAT ASTROGLIAL CELLS AND IN RAT SYNAPTOSOMES

Abstract

Abstract —The brain‐specific antigens 14·3·2, GFA, A5, F3, D1, D2, D3 and C1 were quantitated in a short‐term astroglial cell culture taken as a model of glial cells, and in synaptosomes, synaptosomal membranes and synaptic vesicles as neuronal material. Furthermore, the antigens were quantitated in newborn rat brain, as this served as the starting material for the cell culture. The membrane antigens C1, D1, D2 and D3 were absent from the cultured astroglia, indicating a neuronal origin for these antigens. C1 was enriched 3‐fold in synaptosomes and synaptosomal membranes and more than 10‐fold in synaptic vesicles indicating that this antigen might be a marker protein for nerve endings. The name Synaptin is introduced for this antigen. Conversely, the data on the antigens D1, D2 and D3 indicated that these antigens were not restricted to the synaptosomes although they were of neuronal origin. Trace amounts of the cathodal part of the heterogeneous cytoplasmic antigen 14·3·2 were present in the cell culture, possibly originating from a few contaminating neurons. The cytoplasmic antigens A5 and F3 were found both in the astroglial culture and in the synaptosomal fraction. F3, however, was found in low concentration in the synaptosomes and 3‐fold enriched in newborn rat brain compared to rat brain from 35‐day‐old rats or to 21‐day‐old brain cell cultures. It was therefore regarded as a brain specific fetal antigen. The antigen GFA was highly enriched in the astroglial culture compared to whole brain and only trace amounts were found in the synaptosomal fraction supporting the astroglial origin of this antigen.