Transport adenosine triphosphatase activity in the rat cornea.
The sodium-potassium activated adenosine triphosphatase (NaKATPase) activity of the rat cornea was investigated histochemically using a Pb2+-precipitation technique in which adenosine triphosphate (ATP) is used as substrate and two methods for potassium-dependent para-nitrophenyl-phosphatase (K-NPPase) activity. With all the three techniques used it was demonstrated that the sodium-potassium-activated adenosine triphosphatase (NaK-ATPase) activity is localized in the cell membranes of the endothelium whereas a much weaker activity was observed in the epithelium. When the Pb2+-technique was used, the epithelial cell membranes showed a weaker reaction in the presence of ouabain. This activity was only Mg2+-dependent and was presumably due to an Mg2+-dependent ATPase. The validity of the histochemical techniques for NaK-ATPase activity is discussed. The results emphasize the importance of the endothelium as the main site of Na+ transport in the cornea. Small amounts of the enzyme are also present in the epithelium, which seems to be rich in Mg2+-ATPase. Provided that careful controls are performed, all the methods give consistent results in the cornea.
D009597:4-Nitrophenylphosphatase / Q000032:analysis; D000251:Adenosine Triphosphatases / Q000032:analysis*; D000818:Animals; D001693:Biological Transport, Active; D003315:Cornea / Q000201:enzymology* / Q000648:ultrastructure; D004121:Dimethyl Sulfoxide; D004727:Endothelium / Q000201:enzymology; D004848:Epithelium / Q000201:enzymology; D005260:Female; D006651:Histocytochemistry; D007854:Lead; D008297:Male; D008854:Microscopy, Electron; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism; D013194:Staining and Labeling; D013324:Strontium
D007854:Lead; D012964:Sodium; D009597:4-Nitrophenylphosphatase; D000251:Adenosine Triphosphatases; D011188:Potassium; D004121:Dimethyl Sulfoxide; D013324:Strontium