Nitric Oxide

Abstract

Background Attenuation of myocardial stunning by several angiotensin-converting enzyme (ACE) inhibitors has been demonstrated. However, the signal cascade mediating such protective effect has not been analyzed in detail so far. Methods and Results In a first protocol, we addressed the role of bradykinin and analyzed the effect of the ACE inhibitor ramiprilat without and with added bradykinin B2 receptor antagonist HOE 140 on regional myocardial blood flow (colored microspheres) and function (sonomicrometry). Thirtytwo enflurane/N2O-anesthetized open-chest dogs were subjected to 15 minutes of occlusion of the left circumflex coronary artery (LCx) and 4 hours of subsequent reperfusion. Eight dogs served as placebo controls (group 1), and 8 dogs received ramiprilat (20 ,ug/kg IV) before LCx occlusion (group 2). Eight dogs received a continuous intracoronary infusion of HOE 140 [0.5 ng/(mL. min) IC] during ischemia and reperfusion (group 3), and in 8 dogs HOE 140 was infused continuously during ischemia and reperfusion, starting 45 minutes before the administration of ramiprilat (group 4). Mean aortic pressure was kept constant with an intra-aortic balloon, and heart rate did not change throughout the experimental protocols. Under control conditions and during myocardial ischemia, posterior transmural blood flow (BF) and systolic wall thickening (WT) were not different in the four groups of dogs. However, at 4 hours of reperfusion, WT was still depressed in groups 1 (10±20% of control [mean±SD]), 3 (-18±12% of control), and 4 (-12±21% of control), whereas WT in group 2 had recovered to 55±20% of control (P<.05 versus group 1). BF at 4 hours of reperfusion was not

Cite this paper

@inproceedings{Ehring2005NitricO, title={Nitric Oxide}, author={Thomas Ehring and Mladen Krajcar}, year={2005} }