Title: EFFECTS OF ISCHEMIC AND Ca PRECONDITIONING ON INTRACELLULAR Ca DYNAMICS IN ISCHEMIA-REPERFUSED RAT HEARTS
Abstract:Ischemic preconditioning (IPC) has been proposed to protect myocardium against ischemia-reperfusion injury in numerous experimental models. Although Ca may play a key role in inducing IPC,the precise ...Ischemic preconditioning (IPC) has been proposed to protect myocardium against ischemia-reperfusion injury in numerous experimental models. Although Ca may play a key role in inducing IPC,the precise mechanism is unclear. We observed changes in intracellular Ca concentration([Ca ])and ventricular contractility in the whole heart during ischemiareperfusion and compared the cardioprotective effects of IPC and Ca preconditioning (CPC). Hearts from Sprague-Dawley rats were perfused in the Langendorff mode and loaded with 4 μmol/L fura-2/AM to measure the fluorescence ratio as an index of[Ca ].Left ventricular pressure and electrocardiograms were simultaneously recorded. Hearts were exposed to 10 minutes of low-flow ischemia,then reperfused.In the IPC group(n=5)hearts were exposed to ischemia twice for 2 min before sustained ischemia. In the CPC group,hearts were exposed to a low Na solution(70 mmol/L;CPLN group,n=7)or a high Ca solution(3.5 mmol/L; CPHC group, n=6) twice for 1 minute to induce Ca influx before sustained ischemia. Transient increase in[Ca ] were observed during preconditioning in all preconditioned groups. The[Ca ]increased signifficantly less in the IPC group than in the control group (n=6)at 1,5 and 10 minutes of ischemia and at 1 minute of reperfusion. The increase in [Ca ]was also signifficantly less at 1 minute of ischemia and at 1 minute of reperfusion in the CPLN group but only at 1 minute of reperfusion in the CPHC group. The rate of recovery in the rate-pressure product on reperfusion was signifficantly higher in all preconditioned groups than in the control group. A transient increase in [Ca ]may trigger IPC, and a reduction in intracellular Ca overload may be involved in the mechanism of cardioprotection in IPC. (Tokyo Jikeikai Medical Journal 2003;118:51-61)Read More
Publication Year: 2003
Publication Date: 2003-03-15
Language: en
Type: article
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