Contractions reverse stress softening in rat esophagus

Strain/stress induced tissue softening is usually referred to irreversible softening. The aim of this study was to investigate whether stress softening in rat esophagus is reversible after potassium chloride (KCl) induced contraction. Three series of inflation-deflation loadings were carried out on esophageal specimens obtained from 20 Wistar rats. All specimens were subjected to the first two series in Ca(2+)-free Krebs solution(Krebs(-)) and then incubated in Ca(2+)-containing Krebs solution (Krebs(+)) for 1 h. Ten specimens were distended to pressure 1.0 kPa and activated with KCl for 3 min. The other ten specimens, however, were distended to 1.0 kPa without KCl activation. Subsequently, after incubation in Krebs(-) for 1 h, all 20 specimens were subjected to the third series testing. The stored energy in the esophageal tissues (hysteresis loop area) and the esophageal wall stiffness were compared between two groups within the three series loadings. Results indicated that incubation in Krebs(+) cannot recover the stress softening induced energy and stiffness loss, but in contrast, these loss were recovered markedly (p < 0.05) after KCl activation. In conclusion, stress softening in rat esophagus is reversible after the activation of KCl-induced contractions. This mechanism could be related to regeneration of tissue properties in rat esophagus.