PASSIVE ELASTIC WALL PROPERTIES IN ISOLATED GUINEA-PIG SMALL-INTESTINE

The aim was to study and compare the passive biomechanical wall proper ties in the isolated duodenum and distal ileum of the guinea pig in vi tro. The organ bath contained a Krebs-Ringer solution with 10(-2) M Mg Cl2 to abolish smooth muscle contractile activity. Stepwise inflation of an intraluminal balloon, in which the cross-sectional area (CSA) wa s 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 e valuate the passive elastic properties. The CSA always reached equilib rium within the 2-min distension period. The CSAs obtained in the dist al ileum were higher than those in the duodenum (P < 0.001). The basal CSA was 17.31 +/- 1.14 mm(2) and 12.96 +/- 0.42 mm(2) 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 mm(2) and 36.86 +/- 1.76 mm(2) for the duodenum (P < 0.01). The circumferential wall tens ion-strain distributions showed an exponential behavior that accorded well with the equation Y = exp(a + bX) with determination coefficients of 0.96 +/- 0.01 and 0.99 +/- 0.00 in the duodenal segments in the di stal ileal segments, respectively. The values of a (intercept with the y-axis) were 0.54 +/- 0.11 and -0.35 +/- 0.19 for the duodenal and il eal segments, respectively (P < 0.001). The slope of the curves (b val ues) 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 prop erties were found between the proximal and distal small intestine.