ATP-dependent regulation of inwardly rectifying K+ current in bovine retinal pigment epithelial cells.
Inwardly rectifying K+ current (IKir) in freshly isolated bovine retinal pigment epithelial (RPE) cells was studied in the whole cell recording configuration of the patch-clamp technique. When cells were dialyzed with pipette solution containing no ATP, IKir ran down completely in <10 min [half time (t1/2) = 1.9 min]. In contrast, dialysis with 2 mM ATP sustained IKir for 10 min or more. Rundown was also prevented with 4 mM GTP or ADP. When 0.5 mM ATP was used, IKir ran down by approximately 71%. Mg2+ was a critical cofactor because rundown occurred when the pipette solution contained 4 mM ATP but no Mg2+ (t1/2 = 1.8 min). IKir also ran down when the pipette solution contained 4 mM Mg2+ + 4 mM 5'-adenylylimidodiphosphate (t1/2 = 2.7 min) or 4 mM adenosine 5'-O-(3-thiotriphosphate) (t1/2 = 1.9 min), nonhydrolyzable and poorly hydrolyzable ATP analogs, respectively. We conclude that the sustained activity of IKir in bovine RPE requires intracellular MgATP and that the underlying mechanism may involve ATP hydrolysis.
Hughes
B A
BA
Departments of Ophthalmology and Physiology, University of Michigan, Ann Arbor, Michigan 48105, USA.
Takahira
M
M
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000666:Amphotericin B / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D002586:Cesium / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006706:Homeostasis; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010857:Pigment Epithelium of Eye / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying
D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D002586:Cesium; D001464:Barium; D000266:Adenylyl Imidodiphosphate; C022571:adenosine 5'-O-(3-thiotriphosphate); D000244:Adenosine Diphosphate; D000666:Amphotericin B; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D008274:Magnesium