Faculty Collaboration Database

Modulation of sodium-potassium adenosine triphosphatase in cultured bovine retinal pigment epithelium by potassium. Invest Ophthalmol Vis Sci 1993 Mar;34(3):694-8

Date

03/01/1993

Pubmed ID

8383646

Scopus ID

2-s2.0-0027461336 (requires institutional sign-in at Scopus site)

Abstract

PURPOSE: The aim of the study was to examine the extracellular potassium concentration [K+]o as a modulator of the retinal pigment epithelium (RPE) contribution to ion homeostasis in the subretinal space by measuring sodium-potassium adenosine triphosphatase (Na+/K+ ATPase) pump number and activity in cultured bovine RPE in the presence of different concentrations of extracellular potassium.

METHODS: Pump number was quantified by measuring specific binding of 3H-ouabain to bovine RPE exposed to low (0.5-2.5 mmol) or control (5.0 mmol) [K+]o over 72 hr. Na+/K+ ATPase activity in low and control [K+]o was quantified by measurement of 86Rb+ uptake.

RESULTS: Low [K+]o increased RPE pump number in a dose- and time-dependent manner, with lesser effects on denser than on sparser cultures. [K+]-modulation of pump number was reversible and did not occur in the presence of the protein synthesis inhibitor cycloheximide. In RPE exposed to low [K+]o for 72 hr, pump activity was decreased compared with the control but increased toward control levels when re-exposed to control [K+]o. The total potassium transported per cell was 60% of control in low [K+]o but increased to slightly above control when re-exposed to control [K+]o.

CONCLUSIONS: In cultured RPE cells, both Na+/K+ ATPase pump number and pump activity are affected by changes in [K+]o, with greater modulation in sparser cultures. If similar events occur in situ, the sodium pump in RPE may respond to changes in subretinal potassium ion concentration, especially if the RPE cell number is reduced as in aging or disease.

Author List

Suson JD, Burke JM

Author

John D. Suson MD Assistant Professor in the Ophthalmology and Visual Sciences department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Cattle
Cells, Cultured
Ouabain
Pigment Epithelium of Eye
Potassium
Rubidium Radioisotopes
Sodium-Potassium-Exchanging ATPase