39K NMR measurement of intracellular potassium during ischemia in the perfused guinea pig heart.
The hyperfine shift reagent, TmDOTP5-, was used to resolve the 39K NMR resonances of intra- (Ki+) and extracellular (Ke+) potassium in isolated, perfused guinea pig hearts. [Ki+] as measured by 39K NMR was 25.9 +/- 10.3 mM, compared with 114.4 +/- 10.8 mM as measured by atomic absorption spectroscopy (AAS) using TmDOTP5- as a marker of extracellular space. Thus, only approximately 23% of intracellular potassium was detected by 39K NMR using our experimental conditions. The area of the Ki+ signal increased during early ischemia then returned to baseline levels during reperfusion. In an effort to learn more about the Ki+ not detected by 39K NMR, hearts were perfused with a Rb+-enriched, K+-depleted buffer for an extended period. This resulted in loss of the entire 39K NMR signal, and Ki+, as measured by AAS, decreased from approximately 60 to approximately 6 to 7 micromol/g wet weight. When K+-depleted hearts were subjected to global ischemia, a small 39K NMR signal reappeared, suggesting that at least a portion of the nonexchangeable Ki+ becomes detectable by NMR during ischemia. This newly visible K+ signal subsequently dissipated during reperfusion of ischemic hearts. We conclude that ischemia induces changes in the NMR visibility of 39K in perfused guinea pig hearts.
Radford
N B
NB
University of Texas Southwestern Medical Center, Dallas, USA.
Babcock
E E
EE
Richman
A
A
Szczepaniak
L
L
Malloy
C R
CR
Sherry
A D
AD
D000818:Animals; D006168:Guinea Pigs; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D017202:Myocardial Ischemia / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; D010477:Perfusion; D011188:Potassium / Q000378:metabolism*; D013054:Spectrophotometry, Atomic; D013932:Thulium
D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; C069929:thulium(III) 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetramethylenephosphonate; D013932:Thulium; D011188:Potassium