[Alkaline phosphatase activity in human gliomas as revealed by light and electron microscopy]

Precise localization of alkaline phosphatase (ALPase) activity in human gliomas was examined by light and electron microscopy in association with malignant transformation, paying much attention to changes in blood-brain barrier. Materials used were eight cases of gliomas four of which were astrocytoma grade 2, one astrocytoma grade 3, and three, glioblastoma multiforme, respectively. Specimens were quickly fixed in cacodylate-buffered 2% glutaraldehyde at 4 degrees C for 1 hour and rinsed overnight in the same buffer. Frozen or nonfrozen sections (40 microns thick) were made and incubated at 20 degrees C for 40 min, and processed for light and electron microscopy. For the demonstration of ALPase activity, the lead citrate method (Mayahara et al., 1967) was employed. By light microscopy, ALPase activity appeared to be mainly restricted to the capillary wall. By electron microscopy, reaction product representing ALPase activity was distributed in the plasma membrane of endothelial cells both in astrocytomas and in glioblastoma. In astrocytoma grade 2, activity was primarily localized along the abluminal surface of endothelial cells. In glioblastoma, on the other hand, ALPase activity was positive on the luminal surface of the plasma membrane of endothelial cells. It was much more intense than that along the abluminal surface. Regional differences in enzyme cytochemistry may represent functional heterogeneity in the endothelial cell membrane. In brain tumors, changes in distribution pattern of enzyme activity were visualized in the present study in association with glioma malignancy. This might represent a functional aspect of changes in blood-brain barrier in human glioma tissue during course of its malignant transformation.