Stretch-activated ion channel blocker gadolinium attenuates ischemic ST-segment elevation in canine myocardium.
Regional transmural ischemia causes both ST-segment elevation and systolic elongation (bulging) of the myocardium. Mechanical stretch might alter the transmembrane potential via stretch-activated ion channels (SAC); however, the role of SAC on ischemic ST-segment elevation has not yet fully studied. The present study investigated the role of SAC in the genesis of ischemic ST-segment elevation in the in-vivo canine heart. In 6 anesthetized dogs, an extracorporeal conduit connected to the left anterior descending coronary artery was occluded for 5 min before and after the intracoronary infusion of gadolinium (Gd, 500 micromol/min). To eliminate the effect of ischemic preconditioning, the bypass was occluded for 5 min before the experiment. Percent systolic shortening (%SS) and percent systolic elongation (%bulging) were measured using a pair of ultrasonic dimension crystals. A unipolar epicardial ECG was monitored at the center of the ischemic area for the measurement of the ST-segment level. At the end of coronary occlusion, there was no difference in the reduction of %SS or the increase of %bulging between before and after infusion of Gd. ST-segment elevation, however, was significantly attenuated by the infusion of Gd. These data demonstrated that the activation of SAC is one cause of ischemic ST-segment elevation.
Shimada
M
M
Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan. shimada-m@kitasato.or.jp
Nakamura
Y
Y
Iwanaga
S
S
Asakura
K
K
Hattori
S
S
Takahashi
M
M
Ogawa
S
S
D000818:Animals; D003327:Coronary Disease; D004285:Dogs; D004562:Electrocardiography / Q000187:drug effects*; D005260:Female; D005682:Gadolinium / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006439:Hemodynamics; D007473:Ion Channels / Q000037:antagonists & inhibitors*; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D009200:Myocardial Contraction; D017202:Myocardial Ischemia; D015424:Reperfusion
D007473:Ion Channels; D005682:Gadolinium