The incremental Young's moduli in the rat small intestine caused by

Biomechanical remodelling of the rat small intestineafter treatment with epidermal growth factor (EGF) subcutaneously for 2 days(n=6), 4 days (n=6), 7 days (n=6), and 14 days (n=4) was studied. Theincremental circumferential, longitudinal and cross moduli close to the invivo state were computed from bi-axial test data (combined inflation andaxial stretching) by a least square method. The moduli in thecircumferential direction and the longitudinal direction differed in allgroups, i.e. the mechanical properties were anisotropic in both normal andEGF-treated rats. Time-dependent variation existed for the Young's moduli inall directions during EGF treatment (P<0.05). The circumferential modulusdecreased during the first 7 days of EGF treatment and it almost remodelledback to that of the control group after 14 days treatment. The incrementalmodulus in the circumferential direction ranged between 17.4kPa and 24.2kPa.The modulus in the longitudinal direction ranged between 22.9kPa and 32.4kPa.The longitudinal modulus after 4 days EGF treatment was significantly largerthan that of control group (P<0.02). The cross modulus decreased during thefirst 4 days of EGF treatment thereafter it increased to a maximum at 7days. The values for the cross moduli were between 4.7kPa and 6.6kPa. Inconclusion, the mechanical properties in the intestinal wall are anisotropicand remodel during treatment with EGF.