Relationship of high energy phosphate concentrations and oxygen consumption in isolated perfused rat hearts *1J. Giesen, H. Kammermeier, Abt. Physiologie, Med. Fak., RWTH Aachen, W. Germany

Whereas activation of ATP-dependent potassium (KATP) channels greatly improves postischemic myocardial recovery, the final effector mechanism for KATP channel-induced cardioprotection remains elusive. RhoA is a GTPase that regulates a variety of cellular processes known to be involved with KATP channel cardioprotection. Our goal was to determine whether the activity of a key rhoA effector, rho kinase (ROCK), is required for KATP channel-induced cardioprotection. Four groups of perfused rat hearts were subjected to 36 min of zero-flow ischemia and 44 min of reperfusion with continuous measurements of mechanical function and 31P NMR high-energy phosphate data: 1) untreated, 2) pinacidil (10 μM) to activate KATP channels, 3) fasudil (15 μM) to inhibit ROCK, and 4) both fasudil and pinacidil. Pinacidil significantly improved postischemic mechanical recovery [39 ± 16 vs. 108 ± 4 mmHg left ventricular diastolic pressure (LVDP), untreated and pinacidil, respectively]. Fasudil did not affect reperfusion LVDP (41 ± 13 mmHg) but completely blocked the marked improvement in mechanical recovery that occurred with pinacidil treatment (54 ± 15 mmHg). Substantial attenuation of the postischemic energetic recovery was also observed. These data support the hypothesis that ROCK activity plays a role in KATP channel-induced cardioprotection.

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Comparative Anti-Ischemic Effects of Dihydropyridine Calcium Antagonists in Isolated Perfused Rat Hearts: Relationship of Cardiodepression and Cardioprotection

Pharmacology ◽

10.1159/000138652 ◽

1990 ◽

Vol 40 (3) ◽

pp. 137-149 ◽

Cited By ~ 4

Author(s):

Gary J. Grover ◽

Steven Dzwonczyk ◽

Paul G. Sleph

Keyword(s):

Calcium Antagonists ◽

Rat Hearts ◽

Perfused Rat Hearts ◽

Relationship Of ◽

Isolated Perfused Rat Hearts

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NMR-visible ATP and Pi in normoxic and reperfused rat hearts: a quantitative study

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1991.260.1.h6 ◽

1991 ◽

Vol 260 (1) ◽

pp. H6-H12 ◽

Cited By ~ 5

Author(s):

S. M. Humphrey ◽

P. B. Garlick

Keyword(s):

Chemical Analysis ◽

31P Nmr ◽

Ischemia Reperfusion ◽

High Energy ◽

High Energy Phosphates ◽

Rat Hearts ◽

External Standard ◽

Perfused Rat Hearts ◽

Krebs Buffer ◽

Isolated Perfused Rat Hearts

Nuclear magnetic resonance (NMR) spectroscopy detects only free, unbound metabolites. We have therefore compared the free high-energy phosphate content of isolated perfused rat hearts (determined by 31P-NMR) with the total high-energy phosphates of the same hearts (determined by chemical analysis) to determine the fractions, if any, that are NMR invisible. Aerobic perfusion (40 min at 37 degrees C, Pi-free Krebs buffer) was followed by 10, 14, or 18 min total global ischemia and 30 min reperfusion (n = 6 in each group). Fully relaxed 31P-NMR spectra (40 scans using 90 degrees pulses at 15-s intervals) were collected at various times throughout the protocol, and the signal intensities of the beta-phosphate of ATP, phosphocreatine (PCr), and Pi were quantified using methylenediphosphonate as an external standard. Hearts were freeze clamped either before ischemia or at the end of reperfusion and were chemically assayed for ATP, PCr, and Pi. After 40 min of normoxia, the ATP and PCr contents determined by NMR were almost identical to the values determined by chemical analysis. However, only 39 +/- 8% of the total Pi was NMR visible. After reperfusion, after 14 or 18 min of ischemia, the proportion of NMR-visible ATP had decreased to 64 +/- 9% (P less than 0.005). After reperfusion after 18 min ischemia, the proportion of NMR-visible Pi had increased to 76 +/- 10% (P less than 0.05). In conclusion, whereas the total cellular content of PCr is always NMR visible, ischemia-reperfusion can alter the fraction of NMR-visible ATP and Pi.

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