caa a22 4500 475833279 CHVBK 20180406123846.0 cr unu---uuuuu 170329e20001201xx s 000 0 eng 10.1023/A:1007814931512 doi (NATIONALLICENCE)springer-10.1023/A:1007814931512 Effects of Magnesium and its Mechanism on the Incidence of Reperfusion Arrhythmias Following Severe Ischemia in Isolated Rat Hearts [Elektronische Daten] [Kuni Miyoshi, Masayuki Taniguchi, Shingo Seki, Seibu Mochizuki] Magnesium sulfate (Mg) has been widely used for the treatment of ventricular arrhythmias (VF) in patients with coronary artery disease. However, the mechanisms of prevention on the incidence of VF have not been defined. The aim of study was to investigate the role of Mg in the prevention of VF and the mechanism of those effects. Series 1 studied antiarrhythmic effects on VF. Isolated rat hearts were perfused in the working heart mode with Krebs'-Henseleit bicarbonate buffer (KHB). Whole heart ischemia was induced by a one-way ball valve with 300 beats/min electrical pacing for 10 minutes followed by 20 minutes of aerobic reperfusion. After control perfusion, Mg was added from 5 minutes before ischemia and was continued to the end of ischemia (1.2 mM for the control group and 2.4, 3.6, 4.8, and 9.6 mM for the study animals) or during reperfusion (3.6 mM). Left ventricular pressure, aortic flow, and ECG were monitored. Series 2 studied the effect of Mg on [Ca2+]i. Hearts were perfused by the Langendorff mode and were loaded with 4 μM of Fura 2/AM as a [Ca2+]i indicator. Ca2+ was monitored using the ratio of Fura-2 fluorescence intensity at excitation wavelengths of 340 and 380 nm. The hearts were subjected to a 20 minutes of low-flow ischemia followed by 20 minutes of aerobic reperfusion. Then 3.6 mM Mg was added to the KHB medium during ischemia. The duration of VF was significantly suppressed in the 2.4, 3.6, and 4.8 mM/L Mg-added groups (472 ± 173, 779 ± 159, and 525 ± 202 second, respectively) when compared with the control group (1200 seconds). Magnesium sulfate suppressed the fluorescence ratio of the diastolic Ca2+ level at the end of 20 minutes of ischemia from 40.5 ± 3.6% to 9.0 ± 1.0% (P ≤0.05 vs. control hearts). These results suggested that Mg had a beneficial effect on VF and that the optimal Mg concentration was between 2.4 and 4.8 mM. The mechanism of the prevention of VF by Mg could be through the inhibition of [Ca2+]i retention during ischemia. Kluwer Academic Publishers, 2000 magnesium nationallicence ischemia nationallicence reperfusion arrhythmia nationallicence intracellular Ca2+ nationallicence Miyoshi Kuni Division of Cardiology, Department of Internal Medicine, Aoto Hospital, The Jikei University School of Medicine, Tokyo, Japan aut Taniguchi Masayuki Division of Cardiology, Department of Internal Medicine, Aoto Hospital, The Jikei University School of Medicine, Tokyo, Japan aut Seki Shingo Division of Cardiology, Department of Internal Medicine, Aoto Hospital, The Jikei University School of Medicine, Tokyo, Japan aut Mochizuki Seibu Division of Cardiology, Department of Internal Medicine, Aoto Hospital, The Jikei University School of Medicine, Tokyo, Japan aut Cardiovascular Drugs and Therapy Kluwer Academic Publishers 14/6(2000-12-01), 625-633 0920-3206 14:6<625 2000 14 10557 https://doi.org/10.1023/A:1007814931512 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1007814931512 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Miyoshi Kuni Division of Cardiology, Department of Internal Medicine, Aoto Hospital, The Jikei University School of Medicine, Tokyo, Japan aut NATIONALLICENCE 700 1- Taniguchi Masayuki Division of Cardiology, Department of Internal Medicine, Aoto Hospital, The Jikei University School of Medicine, Tokyo, Japan aut NATIONALLICENCE 700 1- Seki Shingo Division of Cardiology, Department of Internal Medicine, Aoto Hospital, The Jikei University School of Medicine, Tokyo, Japan aut NATIONALLICENCE 700 1- Mochizuki Seibu Division of Cardiology, Department of Internal Medicine, Aoto Hospital, The Jikei University School of Medicine, Tokyo, Japan aut NATIONALLICENCE 773 0- Cardiovascular Drugs and Therapy Kluwer Academic Publishers 14/6(2000-12-01), 625-633 0920-3206 14:6<625 2000 14 10557 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer