Detrimental effects of papaverine on the human internal thoracic artery

Abstract

Objective We sought to determine the effects of papaverine on human and canine internal thoracic artery function and structure. Methods Vascular function was assessed with wire myography, and apoptosis was examined with confocal microscopy in arteries stained with ApopTag. Results Acetylcholine-induced endothelium-dependent relaxation in phenylephrine-precontracted arteries was significantly impaired by papaverine treatment in both human and canine internal thoracic arteries (maximal relaxation: 68.35% ± 7.13% vs 47.5% ± 9.32% in human arteries and 74.8% ± 5.5% vs 34.3% ± 8.5% in canine arteries) but not by incubation with acidified saline solution (pH 3.9, which is equivalent to the pH of 10 −2 mol/L papaverine solution) in canine internal thoracic arteries. Contraction of human internal thoracic arteries to phenylephrine or to U46619 was not significantly affected by papaverine treatment and neither was the contraction of canine internal thoracic arteries to phenylephrine. Total apoptotic endothelial and smooth muscle cells were significantly greater in papaverine-treated human and canine internal thoracic arteries. Conclusions Papaverine impairs endothelial function and triggers apoptosis of endothelial and smooth muscle cells of human and canine internal thoracic arteries. The long-term consequence of this impairment on vascular function is not known. Until this question is answered, it will be prudent to use other vasodilators that are less damaging to the internal thoracic artery for cardiac surgery. 23