BASE‐EXCHANGE ENZYMIC SYSTEM FOR THE SYNTHESIS OF PHOSPHOLIPIDS IN NEURONAL AND GLIAL CELLS AND THEIR SUBFRACTIONS: A POSSIBLE MARKER FOR NEURONAL MEMBRANES¹

Abstract

Abstract— The calcium‐dependent incorporation of L‐[3‐ 14 C]serine and [1,2 −14 C]ethanolamine into the phospholipid of isolated neuronal and glial cells from rabbit brain was studied, and the distribution of the enzymic system among the correspondent subfractions was examined. The neuronal cell‐enriched fraction was found to possess a much higher rate of exchange of both bases than the glial cell‐enriched fraction. Among the sub‐fractions isolated from the neuronal and glial cells, those corresponding to neuronal plasma membranes and microsomes showed a noticeably higher exchange of serine and ethanolamine compared to the corresponding subfractions from glia. Neuronal/glial ratios of about 6–8 were found for the exchange activity in both plasma membrane‐enriched fraction and in microsomes. Synaptosomes and synaptosomal subfractions contained low activities. It is concluded that the calcium‐dependent enzymic system for the exchange of serine, ethanolamine and other nitrogenous bases with endogenous phospholipid is concentrated mostly in the neuronal perikaryal membranes, and could be used as a neuronal marker.