Species specificity of thrombin-induced changed in vascular tone

The authors studied the effects of acetylcholine and human thrombin on the tone of rabbit and dog isolated femoral arteries and aortas with intact endothelium. Acetylcholine produced relaxation in the vessels from both species whereas thrombin relaxed only canine arterial smooth muscle. Thrombin pretreatment increased significantly the relaxant potency of acetylcholine in femoral arteries of dogs. The results suggest an interspecies difference in the thrombin-induced endothelium-dependent vasorelaxation.