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Mechanical-energetic interaction of cardiomyocyte contraction
J Mol Cell Cardiol 22 (Supplement
III) (1990)
F’S61
MECHANICAL-ENEBGETIC INTERACTION OF CARDIOMYOCYTE CONTRACTION Stefmie PllPPing, Horst Rose, HeIrnut Kammermeier. Institute of Physiology, Med. Fat. RWH Aachen Pauwelrstr. D-5100 Aachen, FAG A technique was developed to measure simultanously oxygen consumption and shortening of isolated ventricular myocytes of rat hearts during stimulation. BDM as well as isoprenaline abbreviated the time course of the contraction curve with 0.5 mM [Ca**&. If [Ca”], was 1.8 mM only BDM had a significant effect on time course. The length-time integral (It f of the regiotrated contraction curve was taken as a measure of the “work” performed by the contracting cells and correlated to the oxygen consumption per beat fV,O, ). Stepwise inhibition of the actin-myosin interaction by addition of 2.3- butanedione monoxime f B DM 1 was characterized by a linear relationship between It and V, 0,. Extrapolation to the point of complete inhibi$n of th,’ actinmyosin ATP-ase led to an oxygen consumption due only to the cycling of ions (Ca ,Na ,K ), related to contraction. Basal oxygen consumption was 215 + 14 nl/mgPr* min and V u0, amounted to 0.722 nl/mgP * beat (with 0.5 mM [Ca++] 1, 21 X of which was used for Ioncycling. This value increased to 48 f when [Ca++]e was 1.8 mM.Fhis increase can be interpreted in terms of a Ca++ - desenoetizing effect on the myofilaments due to the enhanced extracellular Ca++. (supported by DFG Ro/755 l-1)
F'S62
TEMPORARY CONTRACTILE BLOCKADE PREVENTS HYPERCONTRACTURE IN ANOXICREOXYGENATED CARDIOMYOCYTES Berthold Siegmund, Thomas Klietz, H Michael Piper. Department of Physiof Diisseldorf, D-4000 Dusseldorf, F.R.G. ology I, University Reoxygenation after 120 min substrate-free anoxia causes sudden hypercontracture in isolated rat cardiomyocytes, but the cells maintain re-establish a sarcolemmal integrity (absence of enzyme release) and nearly normal free energy change of ATP hydrolysis when reoxygenated. It was investigated whether a temporary contractile blockade by 20 mM 2,3-butanedione monoxime (BDM) can prevent reoxygenation-induced hypercontracture. When BDM was present during anoxia and the subsequent 15 min reoxygenation, hypercontracture could be prevented. The anoxic changes of high-energy phosphate contents, the free energy change of ATP hydrolysis and the ultrastructure of the cells remained unaffected. When BDM was applied anoxically immediately prior to reoxygenation, it also prevented hypercontracture. Contracture still remained absent when BDM was washed out after 15 min reoxygenation. The prevention of hypercontracture, energetic recovery and sarcolemmal integrity of cardiomyocytes in anoxia-reoxygenation demonstrate that reoxygenation-induced hypercontracture is not based on an already irreversible cell damage.
P~~3~PICaFspmsEsoFmEma;~rO~~~SB~ LIPIDFAtZOR Jaipaul Singh, Therese Hutton and Jack J. Waring, School of Applied Biology, Lancashire Polytechnic, Preston, England The isolated frog heart was used to investigate the inotropic and chronotropic effects of serun and its lipid extract in the canbined presence of cholinergic and adrenergic antagordsts. Dialysed serun taken from several animal species (e.g. man, cow, pig, rabbit, horse and frog) evoked positive inotropic and chronotropic effects on the isolated spontaneously beating frog heart. Fractionation of seruo on colunns of Sephadex G200-120 resulted in several peaks. Fractions corresponding to large molecular constituents in the region of 60,000-70,000 evoked positive inotropic and chronotropic responses on the heart. Density gradient ultracentrifugation of serum resulted in a lipoprotein fraction which evokes positive inotropic responses. Dialysed serm which was either boiled or boiled and subsequently treated with chymotrypsin to denature protein constituents still retained its bioactivity. Similarly, when lipids were extracted fran serum using activated charcoal the extract elicited a marked increase in contractile force. Hmever, serun which was p-e-incubated with lipase failed to increase wocsrdial contractility. The results indicate the presence of either a large molecular weight blood-borne cardioactive lipid factor or a anal1 canpound bound to a large molecule. One of such substances could be cardiolipin since it can also stimulate the frog heart. s.109
III) (1990)
F’S61
MECHANICAL-ENEBGETIC INTERACTION OF CARDIOMYOCYTE CONTRACTION Stefmie PllPPing, Horst Rose, HeIrnut Kammermeier. Institute of Physiology, Med. Fat. RWH Aachen Pauwelrstr. D-5100 Aachen, FAG A technique was developed to measure simultanously oxygen consumption and shortening of isolated ventricular myocytes of rat hearts during stimulation. BDM as well as isoprenaline abbreviated the time course of the contraction curve with 0.5 mM [Ca**&. If [Ca”], was 1.8 mM only BDM had a significant effect on time course. The length-time integral (It f of the regiotrated contraction curve was taken as a measure of the “work” performed by the contracting cells and correlated to the oxygen consumption per beat fV,O, ). Stepwise inhibition of the actin-myosin interaction by addition of 2.3- butanedione monoxime f B DM 1 was characterized by a linear relationship between It and V, 0,. Extrapolation to the point of complete inhibi$n of th,’ actinmyosin ATP-ase led to an oxygen consumption due only to the cycling of ions (Ca ,Na ,K ), related to contraction. Basal oxygen consumption was 215 + 14 nl/mgPr* min and V u0, amounted to 0.722 nl/mgP * beat (with 0.5 mM [Ca++] 1, 21 X of which was used for Ioncycling. This value increased to 48 f when [Ca++]e was 1.8 mM.Fhis increase can be interpreted in terms of a Ca++ - desenoetizing effect on the myofilaments due to the enhanced extracellular Ca++. (supported by DFG Ro/755 l-1)
F'S62
TEMPORARY CONTRACTILE BLOCKADE PREVENTS HYPERCONTRACTURE IN ANOXICREOXYGENATED CARDIOMYOCYTES Berthold Siegmund, Thomas Klietz, H Michael Piper. Department of Physiof Diisseldorf, D-4000 Dusseldorf, F.R.G. ology I, University Reoxygenation after 120 min substrate-free anoxia causes sudden hypercontracture in isolated rat cardiomyocytes, but the cells maintain re-establish a sarcolemmal integrity (absence of enzyme release) and nearly normal free energy change of ATP hydrolysis when reoxygenated. It was investigated whether a temporary contractile blockade by 20 mM 2,3-butanedione monoxime (BDM) can prevent reoxygenation-induced hypercontracture. When BDM was present during anoxia and the subsequent 15 min reoxygenation, hypercontracture could be prevented. The anoxic changes of high-energy phosphate contents, the free energy change of ATP hydrolysis and the ultrastructure of the cells remained unaffected. When BDM was applied anoxically immediately prior to reoxygenation, it also prevented hypercontracture. Contracture still remained absent when BDM was washed out after 15 min reoxygenation. The prevention of hypercontracture, energetic recovery and sarcolemmal integrity of cardiomyocytes in anoxia-reoxygenation demonstrate that reoxygenation-induced hypercontracture is not based on an already irreversible cell damage.
P~~3~PICaFspmsEsoFmEma;~rO~~~SB~ LIPIDFAtZOR Jaipaul Singh, Therese Hutton and Jack J. Waring, School of Applied Biology, Lancashire Polytechnic, Preston, England The isolated frog heart was used to investigate the inotropic and chronotropic effects of serun and its lipid extract in the canbined presence of cholinergic and adrenergic antagordsts. Dialysed serun taken from several animal species (e.g. man, cow, pig, rabbit, horse and frog) evoked positive inotropic and chronotropic effects on the isolated spontaneously beating frog heart. Fractionation of seruo on colunns of Sephadex G200-120 resulted in several peaks. Fractions corresponding to large molecular constituents in the region of 60,000-70,000 evoked positive inotropic and chronotropic responses on the heart. Density gradient ultracentrifugation of serum resulted in a lipoprotein fraction which evokes positive inotropic responses. Dialysed serm which was either boiled or boiled and subsequently treated with chymotrypsin to denature protein constituents still retained its bioactivity. Similarly, when lipids were extracted fran serum using activated charcoal the extract elicited a marked increase in contractile force. Hmever, serun which was p-e-incubated with lipase failed to increase wocsrdial contractility. The results indicate the presence of either a large molecular weight blood-borne cardioactive lipid factor or a anal1 canpound bound to a large molecule. One of such substances could be cardiolipin since it can also stimulate the frog heart. s.109