Brief pressure overload of the left ventricle preconditions rabbit myocardium against infarction.
BACKGROUND
Several nonischemic stimuli have been shown to precondition myocardium. We investigated cardioprotective effects and underlying mechanisms of brief pressure overload of the left ventricle in this study.


METHODS
Brief pressure overload of the left ventricle was achieved by two 10-minute partial snaring of the ascending aorta so that systolic left ventricular pressure was raised 50% above the baseline value. Ischemic preconditioning was elicited by two 10-minute coronary artery occlusions. Ten minutes after different pretreatments, myocardial infarction was induced by a 60-minute coronary artery occlusion followed by 3-hour reperfusion. Area at risk and myocardial infarct was determined by blue dye injection and triphenyl tetrazolium chloride staining.


RESULTS
The myocardial infarct size, expressed as percentage of area at risk, was significantly reduced in the pressure overload group (15.9% +/- 2.9%, p < 0.001, n = 9) as well as in the ischemic preconditioning group (14.9% +/- 1.9%, p < 0.001, n = 9) versus the control group (30.0% +/- 6.9%, n = 10). Pretreatment with a blocker of stretch-activated ion channels (gadolinium, 40 micromol/kg, intravenous) abolished the protection induced by pressure overload and ischemic preconditioning. Gadolinium itself did not alter the extent of infarct. There was no significant difference in hemodynamics, area at risk, and mortality among all groups of animals.


CONCLUSIONS
Brief pressure overload of the left ventricle by partial snaring of the ascending aorta preconditioned rabbit myocardium against infarction. The underlying mechanism might be related to activation of stretch-activated ion channels.
Division of Cardiovascular Surgery, Department of Surgery, Information Service Center, National Yang-Ming University School of Medicine and Taipei Veterans General Hospital, 201 Shih-Pai Road, Section 2, Taipei, Taiwan 11217. chhuang@vghtpe.gov.tw
Cheng-Hsiung
CH
Huang
Jih-Shiuan
JS
Wang
Shu-Chiung
SC
Chiang
Yi-You
YY
Wang
Shiau-Ting
ST
Lai
Zen-Chung
ZC
Weng
D000818:Animals; D001011:Aorta; D016923:Cell Death; D003250:Constriction; D003327:Coronary Disease / Q000503:physiopathology; D005682:Gadolinium / Q000633:toxicity; D006352:Heart Ventricles; D006439:Hemodynamics; D007473:Ion Channels / Q000187:drug effects; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008465:Mechanoreceptors / Q000187:drug effects; D009203:Myocardial Infarction / Q000473:pathology*; D015428:Myocardial Reperfusion Injury / Q000473:pathology*; D011312:Pressure; D011817:Rabbits; D011897:Random Allocation
D007473:Ion Channels; D005682:Gadolinium