- Email: [email protected]
The effect of BDM on the reperfusion-induced calcium gain after ischaemia
j Mol Cell Cardiol 18 (Supplement 1) (1986)
213 THE EFFECTOF BDM ON THE REPERFUSION-INDUCEDCALCIUMGAIN AFTERISCMAEMIA J.S. Elz and W.G. Nayler: Dept of Medicine, University of Melbourne, Austin Hospital, Victoria, Australia. Reports have suggested that 2,3-Butanedione Monoxime(BDM) may prevent cross-bridge formation. We have studied the effect of BDM on the reperfusion-induced Ca2+ gain and ultrastructural changes after ischaemia. Isolated perfused rat hearts were made globally ischaemic at 37~ for 30 min. They were analysed for Ca2+ content or ultrstructural changes after 0-30 min reperfusion. IOBW~BDM was added for 10 min prior to ischaemia and upon reperfusion, lOBw~BDMwas sufficient to prevent the ischaemia-induced rise in resting tension. The Ca2+ gain upon reperfusion in the presence of BDM was significantly reduced at all times. Removal of BDM after 15 min reperfusion resulted in a rapid rise in Ca2+ (13.54• dry wt within 5 min). After 30 min ischaemia we noted extreme shortening of some sarcomeres and overstretching of others. Reperfusion exacerbated this with the formation of contraction bands and the apparent pulling apart of somesarcomeres and ultimately cells. BDM attenuated these changes. After 30 min ischaemia, although some sarcomeres were contracted, there was no extreme shortening or overstretching. Following 5 min of reperfusion with BDM the cells were intact with relaxed myofibrils. Although we can't exclude other actions Qf BDM, i t appears that contracture may be important in the reperfusion-induced Caz+ gain after 30 min ischaemia in the isolated rat heart.
2 1 4 E F F E C T S OF LYSOLECITHIN ON THE I S C ~ I C MYOCARDIUM. A. Lochner, J.C.N. Kotz~, M. de Villiers, P. Brink. MRC Molecular and Cellular Cardiology 0nit, Department of Medical Physiology and Biochemistry, University of Stellenbosch Medical School, Tygerberg, Republic of South Africa. It has been shown that accumulation of lysophosphoglyeerides in myocardial ischaemia facilitates Ca2 + ingress and contributes to dysrhythmias and cell injury.To evaluate the effects of lysophosphoglyceride accumulation in the ischaemic myoeardium~isolated rat hearts perfused with lysoleeithin ~LL) (
215
SUPEROXIDE DISMUTASE AND CATALASE DO NOT DIRECTLY INHIBIT THE UPTAKE OF CALCIUM ON REOXYGENATION AFTER A PERIOD OF HYPOXIA IN THE RABBIT MYOCARDIUM. M.A. Tones, S.E. Harding, P~. Poole-Wilson. Cardiothoracic Institute, 2 Beaumont Street, London, UK. Modification of the cell membrane brought about by oxygen radical formation has been put forward as a mechanism for the increased influx of Ca 2+ into the myocardium on reoxygenation after a period of hypoxic substrate free perfusion. We have tested whether Ca 2+ influx is directly inhibited by enzymatic scavengers of radicals in the absence of whole blood and at constant coronary blood flow. Ca Z+ uptake was followed using 47Ca2+ and the extracellular space with 51CrEDTA in the arterially perfused interventricular rabbit septum at 35~ and 90 beats/min. Superoxide dismutase and catalase (both at 150 U/ml) were added to the perfusate I0 minutes before reoxygenation during 30 (n=5) and 45 (n=4~ minutes hypoxic substrate free perfusion. No significant effect was observed on Ca Z+ uptake or on the recovery of mechanical function on reoxygenation. The activity of angiotensin converting enzyme was 130 ~ 2 U/m E protein after reoxygenatlon~not different to the value in control tissue of 131 II U/mE protein~indicating that the endothelial cells in this preparation had not been lost during hypoxia. Superoxide dismutase and catalase probably do not cross the cell membrane and do not scavenge radicals generated intracellularly. The reported protection of ischaemic myocardium afforded by these substances may be due to an increase of coronary flow. Supported by the Viscount Royston Fellowship Trust.
7~
213 THE EFFECTOF BDM ON THE REPERFUSION-INDUCEDCALCIUMGAIN AFTERISCMAEMIA J.S. Elz and W.G. Nayler: Dept of Medicine, University of Melbourne, Austin Hospital, Victoria, Australia. Reports have suggested that 2,3-Butanedione Monoxime(BDM) may prevent cross-bridge formation. We have studied the effect of BDM on the reperfusion-induced Ca2+ gain and ultrastructural changes after ischaemia. Isolated perfused rat hearts were made globally ischaemic at 37~ for 30 min. They were analysed for Ca2+ content or ultrstructural changes after 0-30 min reperfusion. IOBW~BDM was added for 10 min prior to ischaemia and upon reperfusion, lOBw~BDMwas sufficient to prevent the ischaemia-induced rise in resting tension. The Ca2+ gain upon reperfusion in the presence of BDM was significantly reduced at all times. Removal of BDM after 15 min reperfusion resulted in a rapid rise in Ca2+ (13.54• dry wt within 5 min). After 30 min ischaemia we noted extreme shortening of some sarcomeres and overstretching of others. Reperfusion exacerbated this with the formation of contraction bands and the apparent pulling apart of somesarcomeres and ultimately cells. BDM attenuated these changes. After 30 min ischaemia, although some sarcomeres were contracted, there was no extreme shortening or overstretching. Following 5 min of reperfusion with BDM the cells were intact with relaxed myofibrils. Although we can't exclude other actions Qf BDM, i t appears that contracture may be important in the reperfusion-induced Caz+ gain after 30 min ischaemia in the isolated rat heart.
2 1 4 E F F E C T S OF LYSOLECITHIN ON THE I S C ~ I C MYOCARDIUM. A. Lochner, J.C.N. Kotz~, M. de Villiers, P. Brink. MRC Molecular and Cellular Cardiology 0nit, Department of Medical Physiology and Biochemistry, University of Stellenbosch Medical School, Tygerberg, Republic of South Africa. It has been shown that accumulation of lysophosphoglyeerides in myocardial ischaemia facilitates Ca2 + ingress and contributes to dysrhythmias and cell injury.To evaluate the effects of lysophosphoglyceride accumulation in the ischaemic myoeardium~isolated rat hearts perfused with lysoleeithin ~LL) (
215
SUPEROXIDE DISMUTASE AND CATALASE DO NOT DIRECTLY INHIBIT THE UPTAKE OF CALCIUM ON REOXYGENATION AFTER A PERIOD OF HYPOXIA IN THE RABBIT MYOCARDIUM. M.A. Tones, S.E. Harding, P~. Poole-Wilson. Cardiothoracic Institute, 2 Beaumont Street, London, UK. Modification of the cell membrane brought about by oxygen radical formation has been put forward as a mechanism for the increased influx of Ca 2+ into the myocardium on reoxygenation after a period of hypoxic substrate free perfusion. We have tested whether Ca 2+ influx is directly inhibited by enzymatic scavengers of radicals in the absence of whole blood and at constant coronary blood flow. Ca Z+ uptake was followed using 47Ca2+ and the extracellular space with 51CrEDTA in the arterially perfused interventricular rabbit septum at 35~ and 90 beats/min. Superoxide dismutase and catalase (both at 150 U/ml) were added to the perfusate I0 minutes before reoxygenation during 30 (n=5) and 45 (n=4~ minutes hypoxic substrate free perfusion. No significant effect was observed on Ca Z+ uptake or on the recovery of mechanical function on reoxygenation. The activity of angiotensin converting enzyme was 130 ~ 2 U/m E protein after reoxygenatlon~not different to the value in control tissue of 131 II U/mE protein~indicating that the endothelial cells in this preparation had not been lost during hypoxia. Superoxide dismutase and catalase probably do not cross the cell membrane and do not scavenge radicals generated intracellularly. The reported protection of ischaemic myocardium afforded by these substances may be due to an increase of coronary flow. Supported by the Viscount Royston Fellowship Trust.
7~