Repercussões motoras em esôfago isolado de ratos sujeitos ao refluxo gastroesofágico não erosivo por modelo cirúrgico ou por exposição simulada ao conteúdo gástrico

Abstract

Gastroesophageal reflux disease (GERD) is characterized by retrograde and repeated flow of gastric contents into the esophagus. This disease is closely related to lower esophageal sphincter relaxation and the increase of gastric acid secretion, which results in dilated intercellular spaces and decrease in transepithelial resistance. The most common type is the non-erosive reflux disease, condition associated with typical symptoms caused by gastric acid reflux, but without visible damages in the esophageal mucosa. The aim of the present work was to evaluate in vitro the motor differences between the esophagus of Wistar rats submitted or not to surgical model of non-erosive reflux. The effects of acute exposition of esophageal tissue to solution which mimic the gastric content was also evaluated. The surgical model of reflux consisted in stomach fundus ligation by suture thread tie and pylorus stenosis. The esophagus of animals submitted to surgical model did show either macroscopic alterations or mass-length ratio when compared to fake non-operated rats (sham). However, there was a significant reduction of contractions induced by muscarinic agonist carbamylcholine (Emax 22.7 ± 4.6 mg/mg of dry tissue vs. 51.9 9 ± 10.4 mg/mg of dry tissue in sham animals, p < 0.05, ANOVA). The response to depolarization induced by high extracellular concentration of K+ was also reduced in operated group when compared to sham animals (Emax 12.4 ± 4.9 vs. 35.4 ± 5.2 mg/mg of dry tissue, respectively; p < 0.05, ANOVA). Through the myeloperoxoxidase activity method was increased the number of neutrophils/mg of esophageal tissue in operated group, 758.2 ± 162.0 neutrophils/mg of tissue, when compared to control group, 362.4±17.8 neutrophils/mg of tissue (p < 0.05, ANOVA). In esophagus filled by acidified physiological solution (pH 1) during 30 minutes no statiscal change in the contraction induced by electrical field stimulation however the combination of the acidified solution with pepsin 1mg/mL and taurodeoxycholate 2mM reduced the esophageal contractions. In conclusion, rat esophagus exposure to gastric content or to an acidified solution show a reduced contractility, which might play important role in pathophysiology GERD.