- Email: [email protected]
Superior recovery of hypertrophied myocardium after cardioplegic arrest
J Mol Cell Cardiol
P34
22 (Supplement
V) (1990)
MECHANISM OF NYOCANDIAL ENZYME LEAKAGE: ROLE OF CELL AND MECHANICAL STRESS OF HF.ARTBEAT DUFXNG REPERFUSION
MEMBRANE
FRAGILITY
BY ISCHEMIA
Hiroshi Takami, Hikaru Matsuda, Motonobu Nishimura, Mitsunorl Kaneko, Kunlo Tagawa, First Dept. of Surgery, Osaka University, Osaka, 553, Japan and Yasunaru Kawashima. Although enzyme leakage is used to assess the efficacy of myocardlal preservation, the mechanism of leakage has not been clarified. Myocardlal damage increaslng latently during ischemia may be disclosed by mechanical stress during reperfuslon, resulting in enzyme leakage. Utilizing isolated perfused rat hearts, we investigated effects of spontaneous heartbeat and pumping stress induced by LV balloon on leakage of myocardial enzymes. Heart was reperfused after lschemia without heartbeat by high K+ medium for 10 min and then heartbeat was resumed by normal Kf medium. The leakage of LDH was biphasic and dominant leakage occured after onset of beating. During the arrested period lactate was fully released, which excluded inadequate myocardlal perfusion. By the pumplog stress, LDH leakage from Kc-arrested heart was little (1.0 U/g/30min) during aerobic perfusion. However, the leakages by pumplog increased after anoxia: 4.6 and 21.0 U/g/30mln after 20 min and 60 min of anoxic perfusion, respectively. Percentage release of LDH and cytoplasmlc AST from myocardium coincided well, while that of mitochondrial AST was about one fifth. We conclude that leakage of cytoplasmic enzymes is accelerated by the stress of heartbeat during reperfuslon under the presence of cell membrane fragility developed during preceding ischemla.
P35 TEMPERATURE
AFFECTS HUMAN SARCOPLASMIC RETICULUM CALCIUM ATPASE Rosalind S Labow, Erin Meek, Paul J Hendry, Wilbert J Keon. Department of Cardiothoracic Surgery, University of Ottawa Heart Institute, Ottawa Civic Hospital, Ottawa, CAN KIY 4E9 In assessing methods of donor heart preservation, human myocardium exposed to prolonged hypothermia has been shown to develop changes in relaxation properties during reperfusion. A state of contracture was apparent at 4’C but to a lesser extent at 12’C which may be attributed to altered calcium metabolism. To further elucidate the effect of hypothermia on myocardial calcium homeostasis, human atria1 appendages were stored for 4-24 hours in saline at 0, 4, 12 and 22°C. They were homogenized from a pool weighing 2.5 g, fractionated by ultracentrifugation to obtain sarcoplasmic reticulum (SR) and mitochondria (M) and assayed for Ca ATPase. The Ca ATPase was concentrated ~10 fold in the SR (I 1.2 micromol P./hr/mg protein) and <2 fold in the M (1.04) when fractionated from the homogenate (0.64). Storage at l>‘C preserved the Ca ATPase the best, whereas at 22’C there was a decrease in the activity after only 4 hours of storage. The appendages which had not been stored were fractionated as well. The fresh frozen homogenate, SR and M were assayed for Ca ATPase at 0, 4, 12, 22 and 37’C in order to determine the temperature coefficient (Q,a). Between 4 and 12’C there was a three-fold change in the Q when compared to 12 and 22’C. These results indicate that myocardial storage temperature affecit recovery of Ca ATPase. Excessively cold temperature led to poor recovery of Ca ATPase function which may be an explanation for abnormal relaxation of stored myocardium.
P36
SIJF-ERIOR RECOVERY OF EWPERTROPEIEDMYOCARDIUH AFl'ER CARDIOPLEGIC ARREST Seth D Blank, Robert S McDonald, James S Titus, Pietro Diviacco, David F Torchiana, Gillian Geffin, Willard M Daggett. Department of Surgery, Massachusetts General Hospital, Boston, MA 02114 USA Protection of the hypertrophied (H) heart during cardioplegic arrest remains a clinical challenge. We studied recovery from cardioplegic arrest in 3 models of myocardial H. H was induced in 7 wk old Sprague-Dawley rats by uninephrectomy plus deoxycorticosterone acetate and high salt diet (D) or abdominal aortic banding (B). D and B were studied 7 wks later and each compared to age-matched sham- (S) and nonoperated (C) controls. Twelve wk old spontaneously hypertensive rats (SHR) and WKY controls were also compared. Isolated working rat hearts were arrested at 8'C for 2h with multidose oxygenated cardioplegia (n=152). Recovery of aortic flow (AF) expressed as %prearrest AF in D, B, S, C, SHR and WKY was 79.3+7.2% (~~0.01 vs. S+C), 70.3+3.2% (p=O.O53 vs. S+C), 60.0+3.4%, 59.4+3.6%, 70.9+2.0%; and 59.7+6.5% (p=O.18). Myocardial ATP and glycogen were not significantly different among groups at pre- or end arrest. Thus, hearts with H recovered at least as well or better than their respective controls. This level of recovery in H may be explained by the shift in isomyosin, from predominantly Vl to the more efficient V3 form, that occurs in pressure overloaded rat hearts. Since in man V predominates and there is no shift with H, the rat may not accurately model hum& disease.
s.12
P34
22 (Supplement
V) (1990)
MECHANISM OF NYOCANDIAL ENZYME LEAKAGE: ROLE OF CELL AND MECHANICAL STRESS OF HF.ARTBEAT DUFXNG REPERFUSION
MEMBRANE
FRAGILITY
BY ISCHEMIA
Hiroshi Takami, Hikaru Matsuda, Motonobu Nishimura, Mitsunorl Kaneko, Kunlo Tagawa, First Dept. of Surgery, Osaka University, Osaka, 553, Japan and Yasunaru Kawashima. Although enzyme leakage is used to assess the efficacy of myocardlal preservation, the mechanism of leakage has not been clarified. Myocardlal damage increaslng latently during ischemia may be disclosed by mechanical stress during reperfuslon, resulting in enzyme leakage. Utilizing isolated perfused rat hearts, we investigated effects of spontaneous heartbeat and pumping stress induced by LV balloon on leakage of myocardial enzymes. Heart was reperfused after lschemia without heartbeat by high K+ medium for 10 min and then heartbeat was resumed by normal Kf medium. The leakage of LDH was biphasic and dominant leakage occured after onset of beating. During the arrested period lactate was fully released, which excluded inadequate myocardlal perfusion. By the pumplog stress, LDH leakage from Kc-arrested heart was little (1.0 U/g/30min) during aerobic perfusion. However, the leakages by pumplog increased after anoxia: 4.6 and 21.0 U/g/30mln after 20 min and 60 min of anoxic perfusion, respectively. Percentage release of LDH and cytoplasmlc AST from myocardium coincided well, while that of mitochondrial AST was about one fifth. We conclude that leakage of cytoplasmic enzymes is accelerated by the stress of heartbeat during reperfuslon under the presence of cell membrane fragility developed during preceding ischemla.
P35 TEMPERATURE
AFFECTS HUMAN SARCOPLASMIC RETICULUM CALCIUM ATPASE Rosalind S Labow, Erin Meek, Paul J Hendry, Wilbert J Keon. Department of Cardiothoracic Surgery, University of Ottawa Heart Institute, Ottawa Civic Hospital, Ottawa, CAN KIY 4E9 In assessing methods of donor heart preservation, human myocardium exposed to prolonged hypothermia has been shown to develop changes in relaxation properties during reperfusion. A state of contracture was apparent at 4’C but to a lesser extent at 12’C which may be attributed to altered calcium metabolism. To further elucidate the effect of hypothermia on myocardial calcium homeostasis, human atria1 appendages were stored for 4-24 hours in saline at 0, 4, 12 and 22°C. They were homogenized from a pool weighing 2.5 g, fractionated by ultracentrifugation to obtain sarcoplasmic reticulum (SR) and mitochondria (M) and assayed for Ca ATPase. The Ca ATPase was concentrated ~10 fold in the SR (I 1.2 micromol P./hr/mg protein) and <2 fold in the M (1.04) when fractionated from the homogenate (0.64). Storage at l>‘C preserved the Ca ATPase the best, whereas at 22’C there was a decrease in the activity after only 4 hours of storage. The appendages which had not been stored were fractionated as well. The fresh frozen homogenate, SR and M were assayed for Ca ATPase at 0, 4, 12, 22 and 37’C in order to determine the temperature coefficient (Q,a). Between 4 and 12’C there was a three-fold change in the Q when compared to 12 and 22’C. These results indicate that myocardial storage temperature affecit recovery of Ca ATPase. Excessively cold temperature led to poor recovery of Ca ATPase function which may be an explanation for abnormal relaxation of stored myocardium.
P36
SIJF-ERIOR RECOVERY OF EWPERTROPEIEDMYOCARDIUH AFl'ER CARDIOPLEGIC ARREST Seth D Blank, Robert S McDonald, James S Titus, Pietro Diviacco, David F Torchiana, Gillian Geffin, Willard M Daggett. Department of Surgery, Massachusetts General Hospital, Boston, MA 02114 USA Protection of the hypertrophied (H) heart during cardioplegic arrest remains a clinical challenge. We studied recovery from cardioplegic arrest in 3 models of myocardial H. H was induced in 7 wk old Sprague-Dawley rats by uninephrectomy plus deoxycorticosterone acetate and high salt diet (D) or abdominal aortic banding (B). D and B were studied 7 wks later and each compared to age-matched sham- (S) and nonoperated (C) controls. Twelve wk old spontaneously hypertensive rats (SHR) and WKY controls were also compared. Isolated working rat hearts were arrested at 8'C for 2h with multidose oxygenated cardioplegia (n=152). Recovery of aortic flow (AF) expressed as %prearrest AF in D, B, S, C, SHR and WKY was 79.3+7.2% (~~0.01 vs. S+C), 70.3+3.2% (p=O.O53 vs. S+C), 60.0+3.4%, 59.4+3.6%, 70.9+2.0%; and 59.7+6.5% (p=O.18). Myocardial ATP and glycogen were not significantly different among groups at pre- or end arrest. Thus, hearts with H recovered at least as well or better than their respective controls. This level of recovery in H may be explained by the shift in isomyosin, from predominantly Vl to the more efficient V3 form, that occurs in pressure overloaded rat hearts. Since in man V predominates and there is no shift with H, the rat may not accurately model hum& disease.
s.12