Effect of lidocaine on contracture, intracellular sodium, and pH in ischemic rat hearts
N. B. Butwell, R. Ramasamy, I. Lazar, A. D. Sherry and C. R. Malloy Department of Radiology, Mary Nell and Ralph B. Rogers Magnetic Resonance Center, University of Texas Southwestern Medical Center, Dallas. The relationships among intracellular Na concentration ([Na+]i), intracellular pH, [ATP], and...
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Veröffentlicht in: | American journal of physiology. Heart and circulatory physiology 1993-06, Vol.264 (6), p.H1884-H1889 |
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Zusammenfassung: | N. B. Butwell, R. Ramasamy, I. Lazar, A. D. Sherry and C. R. Malloy
Department of Radiology, Mary Nell and Ralph B. Rogers Magnetic Resonance Center, University of Texas Southwestern Medical Center, Dallas.
The relationships among intracellular Na concentration ([Na+]i),
intracellular pH, [ATP], and contracture during global ischemia were
studied in isolated, perfused rat hearts. Intracellular Na was monitored by
23Na nuclear magnetic resonance (NMR) spectroscopy using thulium
1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra(methylene phosphonate)
(TmDOTP5-) as the paramagnetic shift reagent. High-energy phosphates and pH
were monitored under the same conditions using 31P-NMR spectroscopy.
Lidocaine (130 microM), a class IB fast Na channel blocker known to protect
ischemic myocardium, prolonged the time to contracture in both unpaced and
paced hearts (240 beats/min). After 10 min of global ischemia in paced
hearts, [Na+]i was lower in the lidocaine-treated group compared with
untreated hearts. The addition of lidocaine also significantly attenuated
the depletion of ATP as well as development of intracellular acidosis. At
the time of contracture, however, there was no difference in [Na+]i or pH
between the two groups. Interestingly, the effect of lidocaine on Na+i
accumulation during ischemia was manifested during the first 5-10 min of
ischemia, while its effect on pH occurred after 9 min. This finding
suggests that a mechanism other than the Na-H exchanger may play a role in
the accumulation of Na+i early in the course of ischemia. |
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ISSN: | 0363-6135 0002-9513 1522-1539 |
DOI: | 10.1152/ajpheart.1993.264.6.h1884 |