ATP depletion causes a reversible decrease in Na+ pump density in cultured ventricular myocytes.
To examine factors contributing to impaired K+ homeostasis induced by prolonged but sublethal ATP depletion, we subjected cultured chick ventricular myocytes to metabolic inhibition with 20 mM 2-deoxy-D-glucose plus 1 mM NaCN for 2 h and then allowed myocytes to recover for 5 days in medium containing 6% fetal calf serum (FCS) or in hormone-supplemented serum-free medium. We measured spontaneous contractions (with a video motion detector), K+ content, K+ uptake, membrane potential, and Na+ pump density ([3H]ouabain binding). Exposure to metabolic inhibition for 2 h caused an acute decrease in Na+ pump site density [8.2 +/- 1.1 to 3.8 +/- 0.8 (SE) pmol/mg protein; n = 9, P < 0.02]. Compared with control cells (no metabolic inhibition, cultured for 5 days in serum-free medium), Na+ pump density remained depressed in cells recovered from metabolic inhibition in serum-free medium (3.0 +/- 0.7 pmol/mg), and this was associated with persistently depressed K+ uptake (54% of control), K+ content (67% of control), and membrane depolarization (-19 +/- 2 mV), a significant decrease in cell number (79% of control), and failure to resume spontaneous contractions. Exposure of cells inhibited for 2 h to culture medium containing 6% FCS resulted in a return of Na+ pump site density toward normal levels by 5 days, associated with recovery of K+ uptake and K+ content, preservation of cell number, and resumption of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)
Ikenouchi
H
H
Department of Medicine, University of Utah School of Medicine, Salt Lake City 84132.
Zhao
L
L
McMillan
M
M
Hammond
E M
EM
Barry
W H
WH
D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D002642:Chick Embryo; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles / Q000737:chemistry / Q000166:cytology; D006487:Hemostasis / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D017202:Myocardial Ischemia / Q000503:physiopathology; D009206:Myocardium / Q000166:cytology* / Q000201:enzymology; D010042:Ouabain / Q000378:metabolism; D011188:Potassium / Q000493:pharmacokinetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism / Q000502:physiology*
D010042:Ouabain; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium