Regional differences in the vascular response of the canine esophagus to vasodilators

The basal blood flow of the proximal and distal body of the esophagus, and that of the lower esophageal sphincter, and the vascular response of these sites to intravenous infusion of nifedipine (1.0 μg/ kg · min) and isoproterenol (0.1 μg/kg · min) were studied. The basal blood flow of the mucosa plus submucosa, muscularis propria, and the whole wall was significantly higher in the lower esophageal sphincter than in the proximal or the distal body. Intravenous nifedipine caused a similar decrease in vascular tone of the mucosa and the muscularis propria in all sites of the esophagus. Isoproterenol infusion significantly decreased the vascular tone of the mucosa with columnar epithelium (i.e., mucosa overlying the lower esophageal sphincter), but not of the mucosa with squamous epithelium (i.e., mucosa overlying the body). In the muscularis propria the vasodilatory effect of isoproterenol and nifedipine was significant at all sites, but this effect was greater in the striated muscle of the body than in the smooth muscle of the lower esophageal sphincter (p < 0.05). Thus, not only do different vasodilators have different effects on the vasculature of the esophagus, but also a single agent may have differing effects on the various sites and layers of this organ.