Cytochemical localization of alkaline phosphatase and Na+, K+-ATPase activities in the blood-brain barrier of Rana esculenta.

Abstract

The ultrastructural distribution of alkaline phosphatase and Na+, K+-ATPase on the brain capillaries in Rana esculenta was investigated. Alkaline phosphatase activity appears both on the luminal and abluminal walls of the endothelial capillary cells; Na+, K+-ATPase is, instead, only present on the abluminal side. This different enzymatic distribution indicates that endothelial cells of the brain capillaries are polarized and the luminal and abluminal endothelial membranes are functionally different. The role of these two enzymatic activities is discussed in relation to the blood-brain barrier.