Passive elastic wall properties in isolated guinea pig small intestine

The aim was to study and compare the passive biomechanical wall properties in the isolated duodenum and distal ileum of the guinea pigin vitro. The organ bath contained a Krebs-Ringer solution with 10^?2 M MgCl₂ to abolish smooth muscle contractile activity. Stepwise inflation of an intraluminal balloon, in which the cross-sectional area (CSA) was measured, provided the distension stimulus. The circumferential wall tension-strain distributions and wall stiffness-strain relations were computed from steady-state values of these measurements in order to evaluate the passive elastic properties. The CSA always reached equilibrium within the 2-min distension period. The CSAs obtained in the distal ileum were higher than those in the duodenum (P<0.001). The basal CSA was 17.31±1.14 mm² and 12.96±0.42 mm² for the distal ileum and the duodenum, respectively (P<0.01). At a maximum pressure of 6 kPa, the CSA of the ileum was 56.63±1.81 mm² and 36.86±1.76 mm² for the duodenum (P<0.01). The circumferential wall tension-strain distributions showed an exponential behavior that accorded well with the equationY=exp(a+bX) with determination coefficients of 0.96±0.01 and 0.99±0.00 in the duodenal segments in the distal ileal segments, respectively. The values ofa (intercept with they-axis) were 0.54±0.11 and ?0.35±0.19 for the duodenal and ileal segments, respectively (P<0.001). The slope of the curves (b values) were 4.34±0.35 in the duodenal and 5.23±0.37 in the ileal segments (0.1>P>0.05). In conclusion, differences in elastic properties were found between the proximal and distal small intestine.