Catalase activity in coronary artery endothelium protects smooth muscle against peroxide damage

Cyclopiazonic acid contracts pig coronary artery de-endothelialized rings, and pretreating the rings with hydrogen peroxide (H2O2) inhibits this contr action (IC50 = 0.097 +/- 0.013 mM). We used the cyclopiazonic acid contract ion to test the novel hypothesis that endothelium can protect underlying sm ooth muscle against luminal H2O2. We perfused the arteries with Krebs' solu tion containing 0.3 or 1 mM H2O2, removing endothelium from the arteries ei ther before or after the perfusion. We then cut rings from them to monitor their contraction to 10 mu M cyclopiazonic acid in a H2O2-free solution. Th e inhibition of the cyclopiazonic acid contraction by perfusion with H2O2 w as significantly less when endothelium was removed after the perfusion than when it was removed before it. The specific activity of catalase in post-n uclear supernatants from freshly isolated endothelium (14.1 +/- 2.7 mu mol/ min/mg protein) was 17 +/- 3-fold greater than in those from smooth muscle (0.83 +/- 0.22 mu mol/min/mg protein). Thus endothelium contained high cata lase activity and protected the underlying smooth muscle against luminal pe roxide. (C) 2000 Elsevier Science B.V. All rights reserved.