Effects of peroxide on contractility of coronary artery rings of differentsizes

Reactive oxygen species (ROS, free radicals) produced during cardiac ischem ia and reperfusion can damage the contractile functions of arteries. The sa rcoplasmic reticulum (SR) Ca2+ pump in coronary artery smooth muscle is ver y sensitive to ROS. Here we show that contractions of de-endothelialized ri ngs from porcine left coronary artery produced by the hormone Angiotensin I I and by the SR Ca2+ pump inhibitors cyclopiazonic acid and thapsigargin co rrelate negatively with the tissue weight. In contrast, the contractions du e to membrane depolarization by high KCl correlate positively. Peroxide als o produces a small contraction which correlates negatively with the tissue weight. When artery rings are treated with peroxide and washed, their abili ty to contract with Angiotensin II, cyclopiazonic acid and thapsigargin dec reases. Thus, the SR Ca2+ pump may play a more important role in the contra ctility of the smaller segments of the coronary artery than in the larger s egments. These results are consistent with the hypothesis that ROS which da mage the SR Ca2+ pump affect the contractile function of the distal segment s more adversely than of the proximal segments.