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)