Purine nucleoside phosphorylase: a histochemical marker for glial cells.

The distribution of purine nucleoside phosphorylase activity has been investigated histochemically in rat and guinea-pig brain. At the light microscopical level, enzyme activity was most pronounced in glial cells in various anatomical regions of the rat brain. In contrast, the guinea-pig brain presented only a weak activity. Endothelial cells of both species were also reactive. These findings were confirmed by electron microscopy. Based upon anatomical position and morphologic characteristics, positive glial cells were identified as astrocytes. Precipitate-rich astrocytic processes could be easily demonstrated in between barely reactive neuronal fibers and around microvessels. A minority of astrocytes was devoid of reaction product. The present method may offer a valuable tool for the histopathological study of several types of disorders in which glial cells play a functional role.