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Multiple forms of the sodium pump with different affinities for digitalis
j Mol Cell Cardiol 18 ( S u p p l e m e n t 3) (1986)
THE INFLUENCEOF CARDIOPLEGIAON B-OXIDATION IN THE ISCHEMICPIG HEART. R.M. Engelman, J.A. Rousou, R.H. Breyer, H. Otani, S.D. Datta, S. Lemeshow, and D.K. Das. University of Connecticut School of Medicine, Farmington, CT 06032. Myocardial energy production is dependent on the B-oxidation of fatty acids for support of optimal mechanical function. B-oxidation has been shown to be inhibited by unmodified myocardial ischemia. The influence of cardioplegia and hypothermia on B-oxidation has not been previously reported. Twenty-nine isolated in-vivo pig heart preparations were subjected to 40 min ischemia and 60 min reperfusion: normothermic ischemic arrest (NIA) - 10 animals; hypothermic ischemic arrest (HIA) - 5; antegrade (coronary artery) hypothermic cardioplegia (CAC) - 7; and retrograde (coronary sinus) hypothermic cardioplegia (CSC) - 7. Fatty acids and nucleotides were assessed. Conclusions: 1) Normothermic ischemia inhibits B-oxidation resulting in markedly lower levels of acetyl CoA and ATP and accumulation of both reducing equivalents (manifested as § NADH/NAD) and cytotoxic long-chain fatty acid esters (acyl CoA and acyl carnitine); 2) hypothermic ischemic arrest without cardioplegia affords intermediate protection of fatty acid metabolism (higher carnitine, CoA, acetyl CoA and lower NADH/NAD, acyl CoA and acyl carnitine) than normothermic ischemia; 3) cardioplegia provides improved preservation of nucleotide and l i p i d metabolism; 4) despite cardioplegic administration, there is a significant increase (p<.05) in reducing equivalents during ischemia comparedto control, indicating inhibition of metabolic processes and less than optimal preservation in CAC and CSC groups.
BRAIN MECHANISMS IN CARDIAC ARRhqTHMIA AND SUDDEN DEATH, M.L. Entman, J.~ Skinner. Departments of Medicine and Neurology, Baylor College of Medicine, Houston, Texas, 77030 U.S.A. Environmental stress and reaction to it are factors in the genesis and outcome of cardiac rhythm disturbances. Conscious pigs, when subjected to coronary occlusion, will manifest ventricular fibrillation (VF) within 20 minutes. VF is prevented by: 1) conditioning to the laboratory, 2) cryo-blockade of the frontal corticalbrainstem pathway, and 3) low concentrations of propanolol injected into the lateral cerebral ventricle. Serial biopsies of the myocardium during a ten day conditioning period to the laboratory showed that vulnerability to ventricular fibrillation correlated extremely well with the degree of activation of phosphorylase (P_/P_+P~) despite similar hemodynamlc status ever the conditioning period. Pa/P.+Pb ~as~al~o been useful in predicting the outcome of the coronary occlusion (likelihood of VF) using other therapeutic parameters; VF is rare with P a /P a+P b < 50~ " We suggest that under conditionsof tonic environmental stress adrenergic stimulation results in increased Pa/Pa+Pb while hemodynamic manifestations are suppressed by coincident high muscarinic tone. The clinical implications of these findings regarding the role of environmental stress in cardiac sudden death will be discussed.
M U L T I P L E F O R M S OF THE S O D I U M P U M P W I T H D I F F E R E N T A F F I N I T I E S F O R D I G I T A L I S
E r l a n d Erdmann, L i n d a a y Brown and K a r l Werdan, Medizinische Klinik I, K l i n i k u m G r o s s h a d e r n ~ D - 8 0 0 0 M~nchen 70~ F e d e r a l R e p u b l i c o f Germany Cardiac glycosides bind specifically with high affinity to the external surface o f (Na t + K + ) - A T P a s e , t h u s inhibiting t h e s o d i u m pump. I n c a r d i a c c e l l membranes from the digitalis-insensitive rat heart, two d i s t i n c t ouabain binding site populations w e r e shown ( K n l , 3 x l O - T M , ~ 1 5 % o f s i t e s ; K . 2 , 3xlO-SM) - o n l y t h e low a f f i n ' t y . 5 s i t e s w e r e c o u p l e d t o m e a s u r a b l e (Na + + K + ) - X T P a s e i n h i b i t i o n ( I C ,s_o_ 4xlo M). I n o t r o p i c e f f e c t s in contracting rat ventricular strips correlated with occupation of the high affinity site; t h e low a f f i n i t y site was coupled w i t h s o d i u m pump i n h i b i t i o n and t o x i c i t y . Neonatal rat heart cells in culture a l s o d i s p l a ~ e d two o u a b a i n b i n d i n g s i t e s (KD1 , 3 x l O ' S M , 8 0 0 0 0 s i t e s / c e l l ; KD2 , 7 x 1 0 - 6 M , 10 u s i t e s / c e l l ) . H o w e v e r , t h e low ~ f f i n i t y site was coupled to i n c r e a s e s i n d e v e l o p e d f o r c e and i n h i b i t i o n o f t h e s o d i u m pump. I t w a s p o s s i b l e t o i n c r e a s e t h e number o f t h e s e b i n d i n g s i t e s by i n c u b a t i n g t h e c e l l s i n l o w K+ medium. I n human c a r d i a c c e l l m e m b r a n e s , e v i d e n c e f o r d i f f e r e n t types of b i n d i n g s i t e s was d e m o n s t r a b l e o n l y i n i n c u b a t i o n m e d i a c o n t a i n i n g K§ and ATP. It is possible that the positive inotropic effect in isolated human p a p i l l a r y m u s c l e s ( ~ 1 0 - 7 M ) i s a r e s u l t o f o c c u p a t i o n o f low a f f i n i t ~ sites in contrast to the in vivo situation where lower concentrations (~IO-~M; high affinity sites ?~-cause increases in cardiac coJltractile force.
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THE INFLUENCEOF CARDIOPLEGIAON B-OXIDATION IN THE ISCHEMICPIG HEART. R.M. Engelman, J.A. Rousou, R.H. Breyer, H. Otani, S.D. Datta, S. Lemeshow, and D.K. Das. University of Connecticut School of Medicine, Farmington, CT 06032. Myocardial energy production is dependent on the B-oxidation of fatty acids for support of optimal mechanical function. B-oxidation has been shown to be inhibited by unmodified myocardial ischemia. The influence of cardioplegia and hypothermia on B-oxidation has not been previously reported. Twenty-nine isolated in-vivo pig heart preparations were subjected to 40 min ischemia and 60 min reperfusion: normothermic ischemic arrest (NIA) - 10 animals; hypothermic ischemic arrest (HIA) - 5; antegrade (coronary artery) hypothermic cardioplegia (CAC) - 7; and retrograde (coronary sinus) hypothermic cardioplegia (CSC) - 7. Fatty acids and nucleotides were assessed. Conclusions: 1) Normothermic ischemia inhibits B-oxidation resulting in markedly lower levels of acetyl CoA and ATP and accumulation of both reducing equivalents (manifested as § NADH/NAD) and cytotoxic long-chain fatty acid esters (acyl CoA and acyl carnitine); 2) hypothermic ischemic arrest without cardioplegia affords intermediate protection of fatty acid metabolism (higher carnitine, CoA, acetyl CoA and lower NADH/NAD, acyl CoA and acyl carnitine) than normothermic ischemia; 3) cardioplegia provides improved preservation of nucleotide and l i p i d metabolism; 4) despite cardioplegic administration, there is a significant increase (p<.05) in reducing equivalents during ischemia comparedto control, indicating inhibition of metabolic processes and less than optimal preservation in CAC and CSC groups.
BRAIN MECHANISMS IN CARDIAC ARRhqTHMIA AND SUDDEN DEATH, M.L. Entman, J.~ Skinner. Departments of Medicine and Neurology, Baylor College of Medicine, Houston, Texas, 77030 U.S.A. Environmental stress and reaction to it are factors in the genesis and outcome of cardiac rhythm disturbances. Conscious pigs, when subjected to coronary occlusion, will manifest ventricular fibrillation (VF) within 20 minutes. VF is prevented by: 1) conditioning to the laboratory, 2) cryo-blockade of the frontal corticalbrainstem pathway, and 3) low concentrations of propanolol injected into the lateral cerebral ventricle. Serial biopsies of the myocardium during a ten day conditioning period to the laboratory showed that vulnerability to ventricular fibrillation correlated extremely well with the degree of activation of phosphorylase (P_/P_+P~) despite similar hemodynamlc status ever the conditioning period. Pa/P.+Pb ~as~al~o been useful in predicting the outcome of the coronary occlusion (likelihood of VF) using other therapeutic parameters; VF is rare with P a /P a+P b < 50~ " We suggest that under conditionsof tonic environmental stress adrenergic stimulation results in increased Pa/Pa+Pb while hemodynamic manifestations are suppressed by coincident high muscarinic tone. The clinical implications of these findings regarding the role of environmental stress in cardiac sudden death will be discussed.
M U L T I P L E F O R M S OF THE S O D I U M P U M P W I T H D I F F E R E N T A F F I N I T I E S F O R D I G I T A L I S
E r l a n d Erdmann, L i n d a a y Brown and K a r l Werdan, Medizinische Klinik I, K l i n i k u m G r o s s h a d e r n ~ D - 8 0 0 0 M~nchen 70~ F e d e r a l R e p u b l i c o f Germany Cardiac glycosides bind specifically with high affinity to the external surface o f (Na t + K + ) - A T P a s e , t h u s inhibiting t h e s o d i u m pump. I n c a r d i a c c e l l membranes from the digitalis-insensitive rat heart, two d i s t i n c t ouabain binding site populations w e r e shown ( K n l , 3 x l O - T M , ~ 1 5 % o f s i t e s ; K . 2 , 3xlO-SM) - o n l y t h e low a f f i n ' t y . 5 s i t e s w e r e c o u p l e d t o m e a s u r a b l e (Na + + K + ) - X T P a s e i n h i b i t i o n ( I C ,s_o_ 4xlo M). I n o t r o p i c e f f e c t s in contracting rat ventricular strips correlated with occupation of the high affinity site; t h e low a f f i n i t y site was coupled w i t h s o d i u m pump i n h i b i t i o n and t o x i c i t y . Neonatal rat heart cells in culture a l s o d i s p l a ~ e d two o u a b a i n b i n d i n g s i t e s (KD1 , 3 x l O ' S M , 8 0 0 0 0 s i t e s / c e l l ; KD2 , 7 x 1 0 - 6 M , 10 u s i t e s / c e l l ) . H o w e v e r , t h e low ~ f f i n i t y site was coupled to i n c r e a s e s i n d e v e l o p e d f o r c e and i n h i b i t i o n o f t h e s o d i u m pump. I t w a s p o s s i b l e t o i n c r e a s e t h e number o f t h e s e b i n d i n g s i t e s by i n c u b a t i n g t h e c e l l s i n l o w K+ medium. I n human c a r d i a c c e l l m e m b r a n e s , e v i d e n c e f o r d i f f e r e n t types of b i n d i n g s i t e s was d e m o n s t r a b l e o n l y i n i n c u b a t i o n m e d i a c o n t a i n i n g K§ and ATP. It is possible that the positive inotropic effect in isolated human p a p i l l a r y m u s c l e s ( ~ 1 0 - 7 M ) i s a r e s u l t o f o c c u p a t i o n o f low a f f i n i t ~ sites in contrast to the in vivo situation where lower concentrations (~IO-~M; high affinity sites ?~-cause increases in cardiac coJltractile force.
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