%0 Journal Article
%A Tamiya, Shigeo
%A Dean, William L.
%A Paterson, Christopher A.
%A Delamere, Nicholas A.
%T Regional Distribution of Na,K-ATPase Activity in Porcine Lens Epithelium
%B Investigative Ophthalmology & Visual Science
%D 2003
%R 10.1167/iovs.03-0287
%J Investigative Ophthalmology & Visual Science
%V 44
%N 10
%P 4395-4399
%@ 1552-5783
%X   purpose. It has been established that Na,K-ATPase activity is higher in lens epithelium than fibers. However, others have suggested the Na,K-ATPase enzyme may be inactive or absent in the central 10% of the epithelium. Studies were conducted to measure and compare Na,K-ATPase specific activity and to examine Na,K-ATPase protein expression in the anterior and equatorial regions of porcine lens epithelium.  methods. Na,K-ATPase activity was determined by measuring the ouabain-sensitive rate of adenosine triphosphate (ATP) hydrolysis. Western blot analysis was used to detect Na,K-ATPase catalytic subunit (α) and glycoprotein subunit (β) protein as well as β-actin which was used as a loading control.  results. Na,K-ATPase specific activity was more than two times higher in the equatorial epithelium than the anterior 50% of the epithelium. However, the abundance of Na,K-ATPase α1 isoform protein was similar in the two regions. Neither the α2 nor α3 Na,K-ATPase isoform could be detected in the anterior or equatorial epithelium, but Na,K-ATPase β1 protein was detected in both regions. In contrast to the observed regional difference in Na,K-ATPase activity, the activity of a different P-type ATPase, plasma membrane Ca-ATPase (PMCA), was not significantly different in the anterior and central epithelium. Western blot analysis indicated the presence of two PMCA isoforms, PMCA2, and PMCA4.  conclusions. Na,K-ATPase activity is significantly higher at the equatorial region of the epithelium compared with the anterior, even though the level of Na,K-ATPase protein is similar in the two regions. It is possible that nonuniform distribution of functional Na,K-ATPase activity contributes to the driving force for circulating solute movement through the lens fiber mass. 
%[ 3/1/2021
%U https://doi.org/10.1167/iovs.03-0287