Electron microscopic demonstration of carbonic anhydrase activity in mouse liver cells

Summary Carbonic anhydrase (CAH) activity was demonstrated ultracytochemically in the mouse liver cells fixed with 1% glutaraldehyde buffered to pH 7.2 with 0.1 M cacodylate buffer containing 0.1 M sucrose and other aldehyde fixatives. After the fixed 25–40 section were incubated in Hansson's incubation medium containing 0.2 M sucrose, the cobalt phosphate formed by the action of CAH was converted to lead phosphate by immersing the incubated sections into 0.1% lead nitrate aqueous solution.The lead phosphate precipitate was observed very well on the plasma membrane of hepatocytes in Disse space and of endothelial cells or erythrocytes, and very slightly on the external coat of microvilli in bili canaliculi.In the tissues fixed with 4% formaldehyde, the deposits were found very barely on the microvilli in the space of Disse and the plasma membrane of the endothelial cells or the erythrocytes.As the -hydroxyadipaldehyde-fixed tissues showed the highest the CAH activity but had not a good preservation of morphology, this fixative is not suitable for the electron microscopic histochemistry of CAH.The tissue incubated in medium containing Diamox exhibited non-specific deposits in all over the cell, which were lost when the tissue was treated in Diamox solution before incubation.