NUCLEOSIDE PHOSPHATASE ACTIVITY IN MEMBRANOUS FINE STRUCTURES OF NEURONS AND GLIA

The reaction product resulting from the hydrolysis of various nucleoside phosphate esters in the Wachstein-Meisel medium at a neutral pH has been localized by means of electron microscopy to various glial and neuronal membranous fine structures. Enzyme activity following the use of adenosine triphosphate as a substrate was localized to the interspace between the plasma membranes of neurons and glial dendrites adjacent to the neuronal cell body, the proximal axon and synaptic terminals. The relationship of this enzymatic activity to the transfer of cations, especially sodium and potassium, as well as to the synthesis of acetylcholine at synapses is discussed. A reaction product was also found in the Golgi apparatus of neurons and although it was most prominent following the use of inosine diphosphate as a substrate, it was also noted with other nucleoside phosphates. In addition, enzymatic activity was noted on the plasma membrane of oligodendroglia, particularly when adenosine triphosphate and cytidine triphosphate were used as substrates.