Journal Article

The effect of streptomycin on stretch-induced electrophysiological changes of isolated acute myocardial infarcted hearts in rats†

Fu Lu, Cao Jun-xian, Xie Rong-sheng, Li Jia, Han Ying, Zhu Li-qun and Dai Ying-nan

in EP Europace

Published on behalf of European Heart Rhythm Association of the European Society of Cardiology (ESC)

Volume 9, issue 8, pages 578-584
Published in print August 2007 | ISSN: 1099-5129
Published online July 2007 | e-ISSN: 1532-2092 | DOI: http://dx.doi.org/10.1093/europace/eum132
The effect of streptomycin on stretch-induced electrophysiological changes of isolated acute myocardial infarcted hearts in rats†

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Aims To explore whether the stretch of ischaemic myocardium could modulate the electrophysiological characteristics, especially repolarization via mechanoelectric feedback (MEF), as well as the effect of streptomycin (SM) on these changes.

Methods Thirty-six wistar rats were randomly divided into four groups: control group (n = 9), SM group (n = 9), myocardial infarction (MI) group (n = 9), and MI + SM group (n = 9). After perfused on Langendorff, the isolated hearts were stretched for 5s by a ballon inflation of 0.2mL. After being stretched, the effect of the stretch was observed for 30s, including the 20, 20–70, 70, and 90% monophasic action potential duration (MAPD), i.e. MAPD20, MAPD20–70, MAPD70, and MAPD90, respectively, premature ventricular beats (PVB), and ventricular tachycardia (VT).

Results The stretch caused a decrease in MAPD20–70 (both P <0.01) and an increase in MAPD90 (both P <0.01) in both control and MI groups. Moreover, the MAPD90 in the MI group had increased more significantly than that in the control group (P <0.05). A concentration of 200 µmol/L of SM had no influence on both MAPD20–70 and MAPD90 of basic state (P > 0.05, except MAPD20–70 between the control and SM groups, P < 0.01), whereas it had reduced the length of MAPD90 (P < 0.05) and inhibited the decrease in MAPD20–70 induced by the inflation. There was a decrease in the tendency of MAPD70 after the stretch (P = NS) and SM had reversed the tendency, whereas MAPD20 had no obvious changes after inflation. The incidence rate of PVB and VT in the MI group was higher than that in the control group after inflation (P < 0.01). The 200 µmol/L SM reduced the incidence rate of PVB, and obviously inhibited the occurrence of VT (P < 0.01).

Conclusions Stretch could alter the electrophysiological activities of myocardium via MEF, which could enhance in acute myocardial infarction and facilitate the generation and maintenance of malignant arrhythmias. SM could significantly inhibit the occurrence of arrhythmias, which may correlate with the effect on blocking stretch-activated ion channels.

Keywords: Streptomycin; Arrhythmia; Monophasic action potential; Infarction; Ion channels; Stretch/mechanoelectric coupling

Journal Article.  3974 words.  Illustrated.

Subjects: Cardiovascular Medicine

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