February 1994
Volume 35, Issue 2
Free
Articles  |   February 1994
Relationship between fluid transport and in situ inhibition of Na(+)-K+ adenosine triphosphatase in corneal endothelium.
Author Affiliations
  • M V Riley
    Eye Research Institute, Oakland University, Rochester, MI 48309.
  • B S Winkler
    Eye Research Institute, Oakland University, Rochester, MI 48309.
  • M I Peters
    Eye Research Institute, Oakland University, Rochester, MI 48309.
  • C A Czajkowski
    Eye Research Institute, Oakland University, Rochester, MI 48309.
Investigative Ophthalmology & Visual Science February 1994, Vol.35, 560-567. doi:
  • Views
  • PDF
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      M V Riley, B S Winkler, M I Peters, C A Czajkowski; Relationship between fluid transport and in situ inhibition of Na(+)-K+ adenosine triphosphatase in corneal endothelium.. Invest. Ophthalmol. Vis. Sci. 1994;35(2):560-567.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract

PURPOSE: To examine the relationship between the activity of the sodium pump of the corneal endothelium and corneal thickness. It was postulated that because inhibition pressure of the stroma decreases as thickness increases, a partially inhibited sodium pump would result in a new steady-state thickness of the cornea when reduced rates of fluid influx and efflux were equal. Measurements of physiologic behavior and biochemical activity were to be made in the same tissue and thus establish the relationship directly. METHODS: Rabbit corneas were superfused with a bicarbonate Ringer solution containing different concentrations of ouabain. Exposure to ouabain was either continuous for 4 hours or for an initial 10 minutes followed by ouabain-free superfusion. Thickness was measured, and, after superfusion, endothelium was removed from the corneas, sonicated, and assayed for Na(+)-K+ adenosine triphosphatase (ATPase) activity without further addition of ouabain to the assay medium. Thickness was also measured during superfusion with suboptimal concentrations of Na+ or HCO3- and with brefeldin A, an inhibitor of protein trafficking. RESULTS: Continuous exposure to ouabain caused corneas to swell, but no new steady-state thickness was reached. At low concentrations, swelling rates increased with time, as did the extent of inhibition of the Na(+)-K+ ATPase. With only a 10-minute exposure to ouabain, swelling rates with 10(-4) M to 10(-5) M decreased with the duration of ouabain-free superfusion. Similar swelling curves were obtained by reductions in Na+ or HCO3- concentrations in the superfusion medium, indicating that partial inhibition of the endothelial fluid transport processes, whether via the Na(+)-K+ ATPase or by suboptimal ionic conditions, led toward a new equilibrium thickness of the cornea. However, when superfusion was continued for more than 4 hours, the corneas exposed for 10 minutes to 3 x 10(-5) M or lower-concentration ouabain showed increasing Na(+)-K+ ATPase activity and began to thin, indicating a recovery of fluid transport capability. This recovery was blocked by addition of brefeldin A during the ouabain-free superfusion. CONCLUSIONS: Inhibition of Na(+)-K+ ATPase by low concentrations of ouabain increases with time. Temporary exposure to ouabain causes swelling at rates that decline with time as ouabain dissociates from enzyme sites. This dissociation, together with the turnover of Na(+)-K+ ATPase in the plasma membrane, can lead to recovery of normal thickness in ouabain-exposed corneas. Twenty percent of Na(+)-K+ ATPase in the endothelium is estimated to be intracellular, and about 20% of the activity can be inhibited without inducing swelling.

×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×