[Histochemical demonstration of glial enzyme activity. I. Normal glia]

The literature data for normal glia enzyme activity are reviewed, with special reference to the specific phosphatases and the nucleoside-phosphatases and their relationship to transport mechanisms and the Golgi apparatus. Their demonstration still presents technical difficulties and is also hindered by substrate affinity variations which influence the histochemical picture; greater activity is sometimes observed in the oligodendrocytes and sometimes in the astrocytes and, in the latter, in different cytoplasma or nucleus structures. Using 32ATP, Hyden has shown the importance of this enzyme as a regulator of neuron K availability and of substrate transport from the capillaries to the nerve cells. Several workers have shown the striking positivity of the ATPase reaction in animal glia, as well as its importance in the sodium pump mechanism. Carboanhydrase is also involved in transport mechanisms. Giacobini has demonstrated high cholinesterase values and an absence of AChE in oligodendrocytes and astrocytes. Lysosome has been proved to be an arylsulphatase site. Phosphorylase is important in glial cell metabolism, since high levels indicate increased glycogen metabolism.