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Regional distribution of Na,K-ATPase activity in porcine lens epithelium.
- Source :
-
Investigative ophthalmology & visual science [Invest Ophthalmol Vis Sci] 2003 Oct; Vol. 44 (10), pp. 4395-9. - Publication Year :
- 2003
-
Abstract
- 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.<br />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 (alpha) and glycoprotein subunit (beta) protein as well as beta-actin which was used as a loading control.<br />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 alpha1 isoform protein was similar in the two regions. Neither the alpha2 nor alpha3 Na,K-ATPase isoform could be detected in the anterior or equatorial epithelium, but Na,K-ATPase beta1 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.<br />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.
- Subjects :
- Adenosine Triphosphate metabolism
Anatomy, Regional
Animals
Blotting, Western
Calcium-Transporting ATPases metabolism
Cell Membrane enzymology
Epithelium enzymology
Isoenzymes metabolism
Lens, Crystalline cytology
Ouabain
Swine
Lens, Crystalline enzymology
Sodium-Potassium-Exchanging ATPase metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0146-0404
- Volume :
- 44
- Issue :
- 10
- Database :
- MEDLINE
- Journal :
- Investigative ophthalmology & visual science
- Publication Type :
- Academic Journal
- Accession number :
- 14507885
- Full Text :
- https://doi.org/10.1167/iovs.03-0287