Na+-K+ ATPase distribution in frog and bovine lenses.
Na+-K+ ATPase activity was measured in the capsule-epithelium and decapsulated frog and bovine lens. The decapsulated lens contained approximately 20% of the whole lens activity in the frog and 30% in the bovine. These values were measured from the aqueous homogenate of the entire decapsulated lens, an approach which may have underestimated the activity by diluting the ouabain-sensitive component in the preparation. Subsequent determinations were done on separate portions of superficial (2 to 3 mm) anterior-equatorial, and posterior bovine cortex. The activities per gram of tissue were enriched with respect to the values for the entire decapsulated bovine lens. These activities were further enriched by a sucrose density gradient centrifugation. The anterior-equatorial cortical segment contained 1.6 times the activity found in the capsule-epithelium. The posterior cortex had a much smaller but statistically significant level of Na+-K+ ATPase. It is unlikely that the observed asymmetry of the anterior-equatorial segment with the posterior cortex is exclusively due to epithelial contamination for the result would require the adherence of 62% of the epithelium. Scanning electron micrographs of 6 decapsulated bovine lenses indicated an average contamination of about 9%. This asymmetry may have a physiological role in assisting the pump mechanism of the epithelium.
Alvarez
L J
LJ
Candia
O A
OA
Grillone
L R
LR
D000818:Animals; D001001:Anura; D002417:Cattle; D004848:Epithelium / Q000201:enzymology; D007904:Lens Cortex, Crystalline / Q000201:enzymology / Q000648:ultrastructure; D007908:Lens, Crystalline / Q000201:enzymology*; D008855:Microscopy, Electron, Scanning; D010042:Ouabain / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014018:Tissue Distribution
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase