The relationship of nucleotidase activity to catecholamine storage sites in adrenomedullary tissue

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Abstract
Tissues were either fixed in 3% glutaraldehyde and treated histochemically to demonstrate nucleotidephosphatase activity and catecholamines or in 2.5% potassium dichromate (pH 4.1) for demonstration of catecholamines. Frozen sections (10 μ) were examined with the light microscope or following the histochemical procedures 1 mm cubes of tissue were treated with 1% OsO4 and prepared for electron microscopy.Light microscopy demonstrates groups of norepinephrine cells in adrenal medullary tissue of cats and rats. Nucleotidetriphosphatase activity is found along nerve fibers, between epinephrine cells and concentrated in norepinephrine cell areas. The same is true for diphosphatase localization but with less intense activity. Nucleotidemono‐phosphatase activity is located primarily at the site of norepinephrine cells.Electron microscopy shows triphosphatase activity along membranes of chromaffin cells and nerve fibers, at canaliculi and nerve terminals, and in sinusoidal cells. Diphosphatase activity is present at similar sites and shows some intracellular activity. Monophosphatase activity is present at cell membranes and intracellularly appears closely related to catecholamine storage granules. It is postulated that since nucleotides are apparently instrumental in the binding of catecholamines, nucleotidephosphatase action effects a mechanism of catecholamine release from the storage sites and permits passage through the cell membranes.