Sch-28080 depletes intracellular ATP selectively in mIMCD-3 cells.
Two H(+)-K(+)-ATPase isoforms are present in kidney: the gastric, highly sensitive to Sch-28080, and the colonic, partially sensitive to ouabain. Upregulation of Sch-28080-sensitive H(+)-K(+)-ATPase, or "gastric" H(+)-K(+)-ATPase, has been demonstrated in hypokalemic rat inner medullary collecting duct cells (IMCDs). Nevertheless, only colonic H(+)-K(+)-ATPase mRNA and protein abundance increase in this condition. This study was designed to determine whether Sch-28080 inhibits transporters other than the gastric H(+)-K(+)-ATPase. In the presence of bumetanide, Sch-28080 (200 microM) and ouabain (2 mM) inhibited (86)Rb(+) uptake (>90%). That (86)Rb(+) uptake was almost completely abolished by Sch-28080 indicates an effect of this agent on the Na(+)-K(+)-ATPase. ATPase assays in membranes, or lysed cells, demonstrated sensitivity to ouabain but not Sch-28080. Thus the inhibitory effect of Sch-28080 was dependent on cell integrity. (86)Rb(+)-uptake studies without bumetanide demonstrated that ouabain inhibited activity by only 50%. Addition of Sch-28080 (200 microM) blocked all residual activity. Intracellular ATP declined after Sch-28080 (200 microM) but recovered after removal of this agent. In conclusion, high concentrations of Sch-28080 inhibit K(+)-ATPase activity in mouse IMCD-3 (mIMCD-3) cells as a result of ATP depletion.
Codina
J
J
Department of Internal Medicine, University of Kansas School of Medicine, Kansas City, Kansas 66160-7350, USA.
Cardwell
J
J
Gitomer
J J
JJ
Cui
Y
Y
Kone
B C
BC
Dubose
T D
TD
D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors*; D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002460:Cell Line; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism*; D007679:Kidney Medulla; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D010042:Ouabain / Q000494:pharmacology; D012413:Rubidium / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D007093:Imidazoles; C035235:Sch 28080; D002034:Bumetanide; D010042:Ouabain; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium