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Phospholipid metabolism in heart membranes
j Mol Cell Cardiol 18 (Supplement 3) (1986) PHOSPHOLIPID METABOLISM IN HEART MEMBRANES. K.J.Kako, M.Kato. Department of Physiology, University of Ottawa, Ottawa, Ontario. Work carried out recently in the laboratories of Katz, Sobel, Dhalla and others indicated that certain functions of heart membranes are significantly affected by alterations in membrane lipid composition. Increased phosphatidylethanolamine degradation in ischemic tissues was observed earlier by Chien et al and was attributed to the activation of phospholipase. Alternatively, membrane lipid changes could be induced by peroxidation as a consequence of free radical formation, since recent evidence suggests the involvement of reactive oxygen intermediates in the ischemia-reperfusion cell injury. The results of our previous studies indicated that the (Na+K+)ATPase activity was depressed and the phospholipid content was reduced in sarcolemmal membranes isolated from the ischemic myocardium. In a more recent study, we found that the activity of membrane-bound (NB+K+)ATPase, prepared from the outer medulla of porcine kidney, was decreased either by incubation in the presence of H202, FeCI3 and ADP, or by exposure to ultraviolet light. At the same time lipid peroxidation was enhanced, and arachidonate in the ethanolamine phosphoglyceride molecules was diminished. Addition of thiourea or dithiothreitol prevented the depression of enzyme activity, while administration of butylated hydroxytoluene ameliorated the lipid change. The results suggest that free radical generation serves as a pathogenetic factor for ischemic membrane damage.
DETERMINANTS OF CARDIACPERFORMANCEUNDERGRADEDHYPOXIAAND GRADEDREOXIGENATION H. Kammermeier,V. Perlitz, E. JUngling. Dept. Physiology RWTHAachen, W. Germany In continuation of previous studies (J. Mol. Cell. Cardiol. 14:267 (1982)) dependence of cardiac performance (P) on energy available from ATP hydrolysis (EATP,free energy change) was investigated with respect to 1. reoxigenation and 2. to the process primarily determining cardiac performance. During graded reoxigenation of isolated rat hearts relationship of P v. EATPwas essentially unchangedas compared to graded hypoxia. Concerning the determinant process the energy demandof sarcolemmal ion transport was reduced by partial depolarisation (K+e: 13.5mM), where the relationship P v. EATP was not changed essentially with graded hypoxia. Thus, sarcolemmal ion transport seemsnot~obewimar~y affected. Under hypoxia and reoxigenation including high K+ conditions cardiac performance could s t i l l be increased by paired stimulation and increased extracellular Ca++. This indicates a sufficient energy level for the contractile system and hence, primary disturbance of EM coupling presumably due to EATP insufficient for regular operation of SR. With high K+ during reoxigenation an altered relationship of P v. EATP indicated persistent disturbance of EM coupling as also observed with reoxigenation in situ. Thus, though most ATP dependentprocesses due to their high efficiency necessarily depend on EATP, the dependenceof SR seems most c r i t i c a l . Supported by DFG
CYTOSOLIC FREE CALCIUM TRANSIENTS INDUCED BY ERGONOVINE IN CULTURED VASCULAR SMOOTH MUSCLE CELLS. H.Kanaide, M.Hasegawa, M.Nakamura. Res Inst Angiecardiol, Cardiovasc Clinic, Faculty of Med, Kyushu Univ. Fukuoka, Japan. Cytosolic calcium transients induced by ergonovine were recorded microfluorometrically in primary cultured rat aortic smooth muscle cells treated with quin 2. Both in the presence and the absence of extracellular calcium, ergonovine induced transient, dose-dependent and double-peaked elevations of cytosolic calcium with similar time course and extent, the first and the second peak being observed at 8 and 20 min, respectively. In the absence of extracellular calcium, the first peak elevations were partially inhibited by phsntolamine or ketanserin dose-dependently, and completely inhibited when phentolamine and ketanserin were added at the same time. The second peak was mostly abolished when cells were pretreated with dinitrophenol, and when cells were treated with ergonovine, dinitrophenol-sensitive calcium storage site was mostly depleted. Thus, ergonovine activates both serotonin receptors and alpha adrenoceptors to induce a release of calcium from the cellular storage sites, and also induces calcium release from mitochondria, which result in the transient and double-peakedelevations of cytosolic calcium in cultured rat aortic vascular smooth muscle cells.
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DETERMINANTS OF CARDIACPERFORMANCEUNDERGRADEDHYPOXIAAND GRADEDREOXIGENATION H. Kammermeier,V. Perlitz, E. JUngling. Dept. Physiology RWTHAachen, W. Germany In continuation of previous studies (J. Mol. Cell. Cardiol. 14:267 (1982)) dependence of cardiac performance (P) on energy available from ATP hydrolysis (EATP,free energy change) was investigated with respect to 1. reoxigenation and 2. to the process primarily determining cardiac performance. During graded reoxigenation of isolated rat hearts relationship of P v. EATPwas essentially unchangedas compared to graded hypoxia. Concerning the determinant process the energy demandof sarcolemmal ion transport was reduced by partial depolarisation (K+e: 13.5mM), where the relationship P v. EATP was not changed essentially with graded hypoxia. Thus, sarcolemmal ion transport seemsnot~obewimar~y affected. Under hypoxia and reoxigenation including high K+ conditions cardiac performance could s t i l l be increased by paired stimulation and increased extracellular Ca++. This indicates a sufficient energy level for the contractile system and hence, primary disturbance of EM coupling presumably due to EATP insufficient for regular operation of SR. With high K+ during reoxigenation an altered relationship of P v. EATP indicated persistent disturbance of EM coupling as also observed with reoxigenation in situ. Thus, though most ATP dependentprocesses due to their high efficiency necessarily depend on EATP, the dependenceof SR seems most c r i t i c a l . Supported by DFG
CYTOSOLIC FREE CALCIUM TRANSIENTS INDUCED BY ERGONOVINE IN CULTURED VASCULAR SMOOTH MUSCLE CELLS. H.Kanaide, M.Hasegawa, M.Nakamura. Res Inst Angiecardiol, Cardiovasc Clinic, Faculty of Med, Kyushu Univ. Fukuoka, Japan. Cytosolic calcium transients induced by ergonovine were recorded microfluorometrically in primary cultured rat aortic smooth muscle cells treated with quin 2. Both in the presence and the absence of extracellular calcium, ergonovine induced transient, dose-dependent and double-peaked elevations of cytosolic calcium with similar time course and extent, the first and the second peak being observed at 8 and 20 min, respectively. In the absence of extracellular calcium, the first peak elevations were partially inhibited by phsntolamine or ketanserin dose-dependently, and completely inhibited when phentolamine and ketanserin were added at the same time. The second peak was mostly abolished when cells were pretreated with dinitrophenol, and when cells were treated with ergonovine, dinitrophenol-sensitive calcium storage site was mostly depleted. Thus, ergonovine activates both serotonin receptors and alpha adrenoceptors to induce a release of calcium from the cellular storage sites, and also induces calcium release from mitochondria, which result in the transient and double-peakedelevations of cytosolic calcium in cultured rat aortic vascular smooth muscle cells.
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