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.
University of Texas Southwestern Medical Center, Dallas, USA.
N B
NB
Radford
E E
EE
Babcock
A
A
Richman
L
L
Szczepaniak
C R
CR
Malloy
A D
AD
Sherry
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