Mechanical Properties and Collagen Content Differ Between Isolated Guinea Pig Duodenum, Jejunum, and Distal Ileum

We compared the stress-strain distributionsobtained from isolated segments of the guinea pigduodenum, jejunum, and distal ileum, and the relationbetween the elastic properties and the collagen content. The segments were immersed in Krebs-Ringersolution containing 10-2 M MgCl2to abolish contractile activity. Stepwise inflation ofan intraluminal balloon in which the cross-sectionalarea (CSA) was measured provided the luminal pressure-loading stimulus.The wall thickness was measured by means of 20-MHzA-mode ultrasound. The stress-strain and the incrementalelastic modulus-strain distributions were derived from the steady-state values of wall thickness,internal radius, and applied pressure. The CSA-pressurerelations and the wall thickness-pressure relations werenonlinear and both differed between the segments (P < 0.01). The stress-strain distributionsshowed an exponential behavior that fitted well to theequation Y = a ⋅ Exp(b ⋅ X) (r2 =0.97 ± 0.01). The intercept with the y axis (a)and the slope of the curves (b) differed between the segments(P < 0.01 and P < 0.05). The collagen contentswere 3.99 ± 0.18 μg/mg, 2.51 ± 0.13μg/mg, and 2.10 ± 0.11 μg/mg in theduodenum, jejunum, and distal ileum, respectively. This differencewas significant among all three locations (P > 0.05).An association was found between the collagen contentand the incremental elastic modulus (stiffness) at a stress level of 70 kPa (P <0.05).