Am J Physiol Cell Physiol AJP: Endocrinology and Metabolism
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Am J Physiol Cell Physiol 275: C1372-C1383, 1998;
0363-6143/98 $5.00
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Vol. 275, Issue 5, C1372-C1383, November 1998

ATP-dependent regulation of inwardly rectifying K+ current in bovine retinal pigment epithelial cells

Bret A. Hughes and Masayuki Takahira

Departments of Ophthalmology and Physiology, University of Michigan, Ann Arbor, Michigan 48105

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 ~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.

patch clamp; potassium channels; adenosine triphosphate


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