Rubidium transport in cultured monkey retinal pigment epithelium.
Rb+ influx was used to assess Na-K-Cl cotransport and Na,K-ATPase activities in cultured monkey retinal pigment epithelium. Bumetanide-sensitive (Na-K-Cl cotransport-mediated) Rb+ influx exceeds ouabain-sensitive (Na,K-ATPase-mediated) Rb+ influx, with these two transporters accounting for approximately 95% of total Rb+ uptake. Half-maximal inhibition of Rb+ influx by bumetanide is attained at 75 nM bumetanide. The bumetanide-sensitive Rb+ influx depends on both extracellular Na+ and Cl-, and is activated by extracellular Rb+ with a relatively high affinity. Na-K-Cl cotransport activity is stimulated (2.5-fold) by increased extracellular osmolarity. Elevated cAMP content and glycolytic inhibition both depress cotransport activity. Cyanide application, however, had very little effect on Na-K-Cl cotransport activity. Monkey retinal pigment epithelial cells, maintained in culture, provide a system in which the activity and regulation of cation transport mechanisms can be examined.
Kennedy
B G
BG
Department of Physiology and Biophysics, Northwest Center for Medical Education, Indiana University School of Medicine, Gary 46408.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology; D008252:Macaca fascicularis; D009994:Osmolar Concentration; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002712:Chlorides; D002034:Bumetanide; D012964:Sodium; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium