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ATP depletion causes a reversible decrease in Na+ pump density in cultured ventricular myocytes
H Ikenouchi1, L Zhao, M McMillan
1Department of Medicine, University of Utah School of Medicine, Salt Lake City 84132.
Abstract:
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)
Insights
Prolonged ATP depletion impairs cardiac cell function by reducing sodium pump density. Fetal calf serum (FCS) aids recovery, restoring potassium homeostasis and cell contractility.
Area of Science:
- Cardiovascular Physiology
- Cellular Metabolism
- Ion Homeostasis
Background:
- Prolonged but sublethal ATP depletion can disrupt cellular function.
- Understanding the factors contributing to impaired potassium (K+) homeostasis is crucial for cardiac health.
Purpose of the Study:
- To investigate the effects of metabolic inhibition on chick ventricular myocytes.
- To identify factors influencing the recovery of K+ homeostasis and cellular function after ATP depletion.
Main Methods:
- Cultured chick ventricular myocytes were subjected to metabolic inhibition using 2-deoxy-D-glucose and NaCN.
- Recovery was assessed in media with or without fetal calf serum (FCS).
- Measurements included spontaneous contractions, K+ content and uptake, membrane potential, and Na+ pump density.
Main Results:
- Metabolic inhibition acutely decreased Na+ pump site density.
- Recovery in serum-free medium resulted in persistently depressed K+ uptake, K+ content, membrane depolarization, reduced cell number, and failed contractions.
- Recovery in FCS-containing medium restored Na+ pump density, K+ uptake, K+ content, cell number, and spontaneous contractions.
Conclusions:
- Sublethal ATP depletion severely impairs cardiac myocyte function and K+ homeostasis.
- Fetal calf serum is essential for the recovery of Na+ pump density, K+ homeostasis, and cellular function in myocytes recovering from metabolic stress.