The effect of cyclooxygenase inhibition on vasomotion of proximal coronary arteries with endothelial damage.

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Abstract
Vasomotion of the proximal branches of the left coronary artery was studied in an intact anesthetized canine preparation after injury to the endothelium of the left anterior descending branch of the left coronary artery (LAD) with a balloon angioplasty catheter. The dimensions of the left coronary artery were examined by quantitative angiography and LAD flow was measured by determining intracoronary 133Xe washout. Thirty minutes after endothelial damage alone dimensions of the LAD remained unchanged. In five dogs continued observation for a total of 120 min revealed no significant change in dimensions of the LAD. In another group of five dogs, after the administration of 5 mg/kg indomethacin there was a progressive reduction in cross-sectional area of the LAD by 60, 90, and 105 min (37%, 42%, and 50%, respectively, p less than .05). No significant change in the dimensions of the undamaged left circumflex artery was noted after the administration of indomethacin. The effect of another cyclooxygenase inhibitor (4 mg/kg meclofenamate) on endothelial damage to the LAD in an additional four dogs was also examined. Again significant reduction of the cross-sectional area of the LAD was seen at 60 and 120 min (40% and 44%, respectively, p less than .05). Heart rate and blood pressure were unchanged throughout the experiment in control and indomethacin-treated dogs. Mean blood pressure rose slightly after administration of meclofenamate (from 80 +/- 5 to 98 +/- 7 at 120 min, p less than .05). These data indicate that the combination of endothelial injury and cyclooxygenase inhibition with indomethacin or meclofenamate results in proximal coronary artery vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)