MECHANICAL-PROPERTIES AND COLLAGEN CONTENT DIFFER BETWEEN ISOLATED GUINEA-PIG DUODENUM, JEJUNUM, AND DISTAL ILEUM

We compared the stress-strain distributions obtained from isolated seg ments of the guinea pig duodenum, jejunum, and distal ileum, and the r elation between the elastic properties and the collagen content. The s egments were immersed in Krebs-Ringer solution containing 10(-2) M MgC l2 to abolish contractile activity. Stepwise inflation of an intralumi nal balloon in which the cross-sectional area (CSA) was measured provi ded the luminal pressure-loading stimulus. The wall thickness was meas ured by means of 20-MHz A-mode ultrasound. The stress-strain and the i ncremental elastic modulus-strain distributions were derived from the steady-state values of wall thickness, internal radius, and applied pr essure. The CSA-pressure relations and the wall thickness-pressure rel ations were nonlinear and both differed between the segments (P < 0.01 ). The stress-strain distributions showed an exponential behavior that fitted well to the equation Y = a . Exp(b . X) (r(2) = 0.97 +/- 0.01) . The intercept with the y axis (a) and the slope of the curves (b) di ffered between the segments (P < 0.01 and P < 0.05). The collagen cont ents were 3.99 +/- 0.18 mu g/mg, 2.51 +/- 0.13 mu g/mg, and 2.10 +/- 0 .11 mu g/mg in the duodenum, jejunum, and distal ileum, respectively. This difference was significant among all three locations (P > 0.05). An association was found between the collagen content and the incremen tal elastic modulus (stiffness) at a stress level of 70 kPa (P < 0.05) .