SYSTEMIC TREATMENT WITH EPIDERMAL GROWTH-FACTOR IN THE RAT - BIOMECHANICAL PROPERTIES OF THE GROWING SMALL-INTESTINE

Prolonged treatment with epidermal growth factor (EGF) in the rat prov ides an experimental model to growth of the gastrointestinal tract. We treated female Wistar rats for 0 (n - 15), 1 (n = 8), 2 (n = 8), and 4 (n = 8) weeks with subcutaneous EGF (150 mu g . kg(-1) day(-1)). Seg ments were taken from locations at 10, 50 and 90% along the length of the small intestine, weighed, the wall thickness was measured and the luminal cross-sectional area and passive biomechanical properties were assessed using impedance planimetry. In addition, the wall compositio n was evaluated on histological sections. The weight of the total smal l intestine and of the three segments (measured in mg cm-l) increased with the duration of the EGF treatment due to mucosal and muscular gro wth. After 1 week of treatment the wall thickness increased. After 2 w eeks of treatment the cross-sectional area began to increase. The circ umferential stress-strain distributions revealed translation of the cu rves to the right in the graphs implying reduced wall stiffness during EGF treatment. In conclusion EGF treatment for 1 to 4 weeks caused a time-dependent increase in intestinal weight. The growth was character ized by increased wall thickness, increased cross-sectional area and r educed wall stiffness.