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Isoforms of Na,K-ATPase in rat lens epithelium and fiber cells.
Invest Ophthalmol Vis Sci. 1996 Jul; 37(8):1502-8.IO

Abstract

PURPOSE

The lens epithelium is thought to conduct Na-K transport for the entire lens cell mass. Lens fibers have a poor ion transport capacity. The authors tested whether different Na,K-ATPase polypeptides are expressed in the two cell types and whether both cells have the machinery needed for ongoing Na,K-ATPase expression as judged by the presence of mRNA for the Na,K-ATPase alpha subunit.

METHODS

Membranes were isolated from adult rat lens epithelium or fibers, and Western blot experiments were conducted for Na,K-ATPase alpha 1, alpha 2, and alpha 3 polypeptides. Total RNA was isolated from adult rat lens epithelium or fiber cells, and Northern analysis was conducted for Na,K-ATPase alpha 1, alpha 2, and alpha 3 mRNA. Some experiments were conducted using fiber cells from neonatal (3-day-old) rat lenses.

RESULTS

Multiple isoforms of Na,K-ATPase were detected in adult rat lens epithelium. Judged by Northern blot band intensity, mRNA for Na,K-ATPase alpha 1 and alpha 2 was more abundant than for alpha 3 mRNA. By Western blot, Na,K-ATPase alpha 1, alpha 2, and alpha 3 polypeptides were observed as sharp bands at 100 to 108 kDa. In fiber cells, only Na,K-ATPase alpha 1 immunoreactive polypeptide was detected. Judged by immunoblot density, the amount of alpha 1 polypeptide was similar in both epithelium and fiber cell material. However, Na,K-ATPase alpha subunit mRNA was not found in adult lens fibers. To test whether Na,K-ATPase synthesis takes place during fiber cell growth, Northern blot analysis was conducted with RNA from neonatal (3-day-old) lens fibers; Na,K-ATPase alpha 1 mRNA was clearly visible.

CONCLUSIONS

Adult rat lens epithelium expresses more than one isoform of Na,K-ATPase catalytic subunit, whereas only the alpha 1 isoform can be detected in fiber cells. In adult rat lens fiber cells, the observation of alpha 1 polypeptide, but no alpha 1 mRNA, suggests that ongoing alpha 1 synthesis is low. Based on the detection of alpha 1 mRNA in neonatal lens fibers, Na,K-ATPase synthesis by lens fibers may be higher during cell elongation and growth.

Authors+Show Affiliations

Department of Biochemistry, University of Louisville, Kentucky, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

8675392

Citation

Moseley, A E., et al. "Isoforms of Na,K-ATPase in Rat Lens Epithelium and Fiber Cells." Investigative Ophthalmology & Visual Science, vol. 37, no. 8, 1996, pp. 1502-8.
Moseley AE, Dean WL, Delamere NA. Isoforms of Na,K-ATPase in rat lens epithelium and fiber cells. Invest Ophthalmol Vis Sci. 1996;37(8):1502-8.
Moseley, A. E., Dean, W. L., & Delamere, N. A. (1996). Isoforms of Na,K-ATPase in rat lens epithelium and fiber cells. Investigative Ophthalmology & Visual Science, 37(8), 1502-8.
Moseley AE, Dean WL, Delamere NA. Isoforms of Na,K-ATPase in Rat Lens Epithelium and Fiber Cells. Invest Ophthalmol Vis Sci. 1996;37(8):1502-8. PubMed PMID: 8675392.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Isoforms of Na,K-ATPase in rat lens epithelium and fiber cells. AU - Moseley,A E, AU - Dean,W L, AU - Delamere,N A, PY - 1996/7/1/pubmed PY - 1996/7/1/medline PY - 1996/7/1/entrez SP - 1502 EP - 8 JF - Investigative ophthalmology & visual science JO - Invest Ophthalmol Vis Sci VL - 37 IS - 8 N2 - PURPOSE: The lens epithelium is thought to conduct Na-K transport for the entire lens cell mass. Lens fibers have a poor ion transport capacity. The authors tested whether different Na,K-ATPase polypeptides are expressed in the two cell types and whether both cells have the machinery needed for ongoing Na,K-ATPase expression as judged by the presence of mRNA for the Na,K-ATPase alpha subunit. METHODS: Membranes were isolated from adult rat lens epithelium or fibers, and Western blot experiments were conducted for Na,K-ATPase alpha 1, alpha 2, and alpha 3 polypeptides. Total RNA was isolated from adult rat lens epithelium or fiber cells, and Northern analysis was conducted for Na,K-ATPase alpha 1, alpha 2, and alpha 3 mRNA. Some experiments were conducted using fiber cells from neonatal (3-day-old) rat lenses. RESULTS: Multiple isoforms of Na,K-ATPase were detected in adult rat lens epithelium. Judged by Northern blot band intensity, mRNA for Na,K-ATPase alpha 1 and alpha 2 was more abundant than for alpha 3 mRNA. By Western blot, Na,K-ATPase alpha 1, alpha 2, and alpha 3 polypeptides were observed as sharp bands at 100 to 108 kDa. In fiber cells, only Na,K-ATPase alpha 1 immunoreactive polypeptide was detected. Judged by immunoblot density, the amount of alpha 1 polypeptide was similar in both epithelium and fiber cell material. However, Na,K-ATPase alpha subunit mRNA was not found in adult lens fibers. To test whether Na,K-ATPase synthesis takes place during fiber cell growth, Northern blot analysis was conducted with RNA from neonatal (3-day-old) lens fibers; Na,K-ATPase alpha 1 mRNA was clearly visible. CONCLUSIONS: Adult rat lens epithelium expresses more than one isoform of Na,K-ATPase catalytic subunit, whereas only the alpha 1 isoform can be detected in fiber cells. In adult rat lens fiber cells, the observation of alpha 1 polypeptide, but no alpha 1 mRNA, suggests that ongoing alpha 1 synthesis is low. Based on the detection of alpha 1 mRNA in neonatal lens fibers, Na,K-ATPase synthesis by lens fibers may be higher during cell elongation and growth. SN - 0146-0404 UR - https://www.unboundmedicine.com/medline/citation/8675392/Isoforms_of_NaK_ATPase_in_rat_lens_epithelium_and_fiber_cells_ L2 - https://iovs.arvojournals.org/article.aspx?volume=37&issue=8&page=1502 DB - PRIME DP - Unbound Medicine ER -