19F nuclear magnetic resonance studies of free calcium in heart cells.
19F nuclear magnetic resonance is used in conjunction with 5,5'-difluoro-1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBapta), a fluorinated calcium chelator, to report steady-state intracellular free calcium levels ([Ca2+]i) in populations of resting, quiescent, isolated adult heart cells. 31P nuclear magnetic resonance shows that 5FBapta-loaded cells maintain normal intracellular high-energy phosphates, pH, and free Mg2+. The intracellular free calcium concentration of well perfused, isolated heart cells is 61 +/- 5 nM, measured with 5FBapta, which has a dissociation constant (Kd) for calcium chelation of 500 nM. A similar value is obtained with Quin-MF, another fluorinated calcium chelator with Kd and maximum calcium sensitivity at 80 nM. We find that the steady-state level of intracellular free calcium is increased by decreased extra-cellular sodium concentration, omission of extracellular magnesium, decreased extracellular pH, hyperglycemia, and upon treatment with lead acetate. Further, extracellular ATP caused a large transient increase in [Ca2+]i. Thus, while heart cells maintain a very low level of intracellular free Ca2+, acute alterations in extracellular environment can cause derangement of calcium homeostasis, resulting in measurable increases in [Ca2+]i.
Gupta
R K
RK
Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461.
Wittenberg
B A
BA
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002614:Chelating Agents; D004533:Egtazic Acid / Q000031:analogs & derivatives; D004734:Energy Metabolism; D005461:Fluorine; D005947:Glucose / Q000494:pharmacology; D006321:Heart / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007854:Lead / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009211:Myoglobin / Q000037:antagonists & inhibitors; D009638:Norepinephrine / Q000494:pharmacology; D010758:Phosphorus; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology
D002614:Chelating Agents; D009211:Myoglobin; D010758:Phosphorus; D005461:Fluorine; D007854:Lead; D004533:Egtazic Acid; C039877:5,5'-difluoro-1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D000255:Adenosine Triphosphate; D012964:Sodium; D008274:Magnesium; D005947:Glucose; D002118:Calcium; D009638:Norepinephrine