31P-NMR studies of isolated adult heart cells: effect of myoglobin inactivation.
31P nuclear magnetic resonance (NMR) studies of isolated adult rat heart cells revealed that the cells maintained high-energy phosphates for up to 6 h in polyamide hollow fibers perfused with well-oxygenated nutrient medium. Glucose plus pyruvate superfused heart cells maintained [phosphocreatine]/[ATP] at 1.4 +/- 0.1, internal pH at 7.09 +/- 0.04 (external pH = 7.25), and intracellular free Mg2+ at 0.51 +/- 0.04 mM. In glucose-containing media, hypoxia was accompanied by a reversible decrease in intracellular ATP and phosphocreatine of approximately 50% and 80%, respectively, while the intracellular free Mg2+ was reversibly increased by 40%. However, inhibition of glycolysis by iodoacetate in aerobic pyruvate-containing medium did not significantly alter high-energy phosphate content. Inactivation of intracellular myoglobin with 1-2 mM sodium nitrite, which reduces the steady-state respiratory oxygen consumption rate by 30%, caused a significant (30%) decrease in intracellular phosphocreatine peak, which was reversed upon removal of sodium nitrite. The nitrite-induced decrease in phosphocreatine was also observed in iodoacetate-treated myocytes but not in oligomycin-treated cells. These results indicate that functional myoglobin enhances high-energy phosphate synthesis in well-oxygenated myocytes.
Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461.
R K
RK
Gupta
B A
BA
Wittenberg
D000818:Animals; D002469:Cell Separation; D003470:Culture Media; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology; D009682:Magnetic Resonance Spectroscopy; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009211:Myoglobin / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology; D010477:Perfusion; D010725:Phosphocreatine / Q000378:metabolism; D010758:Phosphorus; D011773:Pyruvates / Q000494:pharmacology; D019289:Pyruvic Acid
D003470:Culture Media; D009211:Myoglobin; D011773:Pyruvates; D010725:Phosphocreatine; D010758:Phosphorus; D019289:Pyruvic Acid; D010100:Oxygen; D009638:Norepinephrine