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Studies on compostion, function and topology of the sarcolemma in cultured heart cells
j Mol Cell Cardiol 19 (Supplement III) (1987) 22OsTUDIES CELLS.
ON COMPOSTION, FUNCTION AND TOPOLOGY OF THE SARCOLEMMA IN CULTURED HEART
Arie Pinson. Laboratory for Myocardial Research, Institute of Biochemistry, The Hebrew University-Hadassah Medical School, Jerusalem, Israel. Cultured heart cells offer an additional tool for studies on the plasma membrane, in particular with respect to kinetic studies in situ. Recently, attention has been focussed on investigation of the non-symmetric lipid composition of the two membrane leaflets. The degree of exposure of sarcolemmal lipids to an enzymatic probe was investigated, employing lactoperoxidase-catalyzed radioiodination. In this symposium-lecture I will summarize research carried out in our laboratory which indicates that dynamic changes in the exposure of phospholipid moieties occur in response to various effectors, such as modification of sarcolemmal lipid composition, ischaemic injury, and iron overload. Correlations between variations in sarcolemmal composition, topology and function will be presented and discussed.
221
THE ROLE OF CYTOSOLIC FREE CALCIUM DURING ANOXIA AND REOXYGENATION. H.M. Piper, A. Allshire, K.S.R Cuthbertson and P. Cohhold. Physiologisches Institut, Universitis D~sseldorf, F.R.G., and Department of Zoology, University of Liverpool, England. Most studies on cellular calcium in the hypoxic/ischemic myocardium do not permit to distinguish between gradual changes in all and more drastic changes in some cells since their methods average on a multicellular preparation. Therefore we used single adult cardiac myocytes from rat injected with aequorin to relate cytosolic free calcium (Ca i) with changes in cell morphology. After approximately i h substrate free anoxia these nonattached cells shortened to a square form. Ca i started to rise only thereafter. After cell shortening, with Ca i below 3 uM, reoxygenation induced a series of Ca i oscillations with subsequent reestablishment of resting Ca i levels. In cells pretreated with 5 mM caffeine, reoxyqenation did not prevent Ca i from rising. At higher Ca i, reoxyqenation rapidly led to terminal overcontracture of the cells. In nominally Ca free medium the series of events was delayed. These results demonstrate (i) that hypoxic cell contracture is not caused by a rise in Ca i. Instead it is probably caused by a critical drop in cytosolic phosphorylation potential. (2) The sarcoplasmic reticulum plays a critical role in enabeling the cell to regain control on cytosolic Ca at Ca i levels up to 1-2 uM, i.e., the level beyond which mitochondria use their respiratory energy rather for Ca accumulation than for ATP production.
222EFFECT OF
VERAPAMIL AND ITS COMBINATION WITH GLUCOS~-YNSULINPOTASSIUM-INFUSION IN DOGS SUBJECTED TO ACUTE MYOCARDIAL ISCHEMIA M. Pissarek, J. NShring, E.-G. Krause, H. Goos, J. Graff, G. Buller, K.-F. Lindenau Cardiovasc. Surg. Karl-Marx-lniv. Leipzig, Centr. Inst. Heart Circ. Res. Acad. Sci. GDR, Berlin The influence of verapamil (V) and its combined application (VG) with a solution containing glucose, insulin and potassium (10 Bg/kg bwt x min, 2.2 M, 50 IU, 20 mM) was investigated in dogs subjected to ligation of the left anterior descending coronary artery for three hours. Heart rate, aortic pressure and parameters of left ventricular hemodynamics were registered and parameters of the energy and glucose metabolism were measured in ischemic (I) and non-isehemic areas (NI) of the hearts. Both interventions (V and VG) reduced the loss of high energy phosphates in l-areas and of creatine phosphate in Nl-areas with equal efficacy.
S.74
ON COMPOSTION, FUNCTION AND TOPOLOGY OF THE SARCOLEMMA IN CULTURED HEART
Arie Pinson. Laboratory for Myocardial Research, Institute of Biochemistry, The Hebrew University-Hadassah Medical School, Jerusalem, Israel. Cultured heart cells offer an additional tool for studies on the plasma membrane, in particular with respect to kinetic studies in situ. Recently, attention has been focussed on investigation of the non-symmetric lipid composition of the two membrane leaflets. The degree of exposure of sarcolemmal lipids to an enzymatic probe was investigated, employing lactoperoxidase-catalyzed radioiodination. In this symposium-lecture I will summarize research carried out in our laboratory which indicates that dynamic changes in the exposure of phospholipid moieties occur in response to various effectors, such as modification of sarcolemmal lipid composition, ischaemic injury, and iron overload. Correlations between variations in sarcolemmal composition, topology and function will be presented and discussed.
221
THE ROLE OF CYTOSOLIC FREE CALCIUM DURING ANOXIA AND REOXYGENATION. H.M. Piper, A. Allshire, K.S.R Cuthbertson and P. Cohhold. Physiologisches Institut, Universitis D~sseldorf, F.R.G., and Department of Zoology, University of Liverpool, England. Most studies on cellular calcium in the hypoxic/ischemic myocardium do not permit to distinguish between gradual changes in all and more drastic changes in some cells since their methods average on a multicellular preparation. Therefore we used single adult cardiac myocytes from rat injected with aequorin to relate cytosolic free calcium (Ca i) with changes in cell morphology. After approximately i h substrate free anoxia these nonattached cells shortened to a square form. Ca i started to rise only thereafter. After cell shortening, with Ca i below 3 uM, reoxygenation induced a series of Ca i oscillations with subsequent reestablishment of resting Ca i levels. In cells pretreated with 5 mM caffeine, reoxyqenation did not prevent Ca i from rising. At higher Ca i, reoxyqenation rapidly led to terminal overcontracture of the cells. In nominally Ca free medium the series of events was delayed. These results demonstrate (i) that hypoxic cell contracture is not caused by a rise in Ca i. Instead it is probably caused by a critical drop in cytosolic phosphorylation potential. (2) The sarcoplasmic reticulum plays a critical role in enabeling the cell to regain control on cytosolic Ca at Ca i levels up to 1-2 uM, i.e., the level beyond which mitochondria use their respiratory energy rather for Ca accumulation than for ATP production.
222EFFECT OF
VERAPAMIL AND ITS COMBINATION WITH GLUCOS~-YNSULINPOTASSIUM-INFUSION IN DOGS SUBJECTED TO ACUTE MYOCARDIAL ISCHEMIA M. Pissarek, J. NShring, E.-G. Krause, H. Goos, J. Graff, G. Buller, K.-F. Lindenau Cardiovasc. Surg. Karl-Marx-lniv. Leipzig, Centr. Inst. Heart Circ. Res. Acad. Sci. GDR, Berlin The influence of verapamil (V) and its combined application (VG) with a solution containing glucose, insulin and potassium (10 Bg/kg bwt x min, 2.2 M, 50 IU, 20 mM) was investigated in dogs subjected to ligation of the left anterior descending coronary artery for three hours. Heart rate, aortic pressure and parameters of left ventricular hemodynamics were registered and parameters of the energy and glucose metabolism were measured in ischemic (I) and non-isehemic areas (NI) of the hearts. Both interventions (V and VG) reduced the loss of high energy phosphates in l-areas and of creatine phosphate in Nl-areas with equal efficacy.
S.74