HYPOTHERMIC CARDIOPLEGIA REDUCES THE OCCURRENCE OF SPONTANEOUS DIASTOLIC MYOFILAMENT MOTION OF THE ISCHEMIC-REPERFUSED RAT-HEART

Spontaneous diastolic myofilament motion of the isolated ischemic-repe rfused rat heart was studied by the technique of laser spectroscopy. S cattered light intensity fluctuations (SLIF) from the exposed surface of the left ventricle of the quiescent perfused (Langendorff) rat hear t were quantified by the autocorrelation function (R(1)F: frequency we ighted by power), and by determining the average power of the SLIF sig nal (PS). The stabilized mean control (+/-SE) R(1)F (mV(2)/s(2)) and P S (mV(2)/s) values were: 0.87+/-0.07 and 21.3+/-1.5 respectively. SLIF were characterized to index the extent of cell Ca2+-loading and the i ntegrity of the sarcoplasmic reticulum (SR) functions by low Na+ and r yanodine perfusions. Low Na+ perfusion significantly increased the R(1 )F values and produced pronounced spectral peaks between 0.5 and 2.5 H z frequency bands; whereas ryanodine (1 mu M) perfusion completely abo lished the SLIF signals. Ischemia (34 degrees C, 60 min.) produced nea rly a 12-fold increase in the R(1)F and PS values accompanied by a fou r-fold increase in the left ventricular end-diastolic pressure (LVEDP) during the reperfusion period (34 degrees C, 30 min.) Pronounced repe rfusion SLIF peaks were evident at the frequency bands between 0.25-5. 0 Hz. Hypothermic (10 degrees C) preservation during ischemia reduced the frequency and the amplitude of the SLIF signals at various frequen cies and prevented the rise in LVEDP. As compared to hypothermia alone , hypothermic cardioplegia offered a slightly better preservation. But hypothermia alone or in combination with cardioplegia failed to compl etely normalize the post-ischemic R(1)F and PS values. The results of this study indicate that hypothermic cardioplegia reduced the occurren ce of spontaneous diastolic intracellular Ca2+ oscillations of the rep erfused rat heart, but failed to completely normalize them.