Tension-strain relations and morphometry of rat small intestine in experimental diabetes

Tension-strain relations and morphometric data were studied in isolated segments of the jejunum and distal ileum in untreated diabetic rats, insulin-treated diabetic rats, and nondiabetic control rats. Diabetes was induced by a single intravenous injection of streptozotocin (28 mg/kg body wt). All injected rats developed hyperglycemia. The experiment was terminated after 28 days and the intestinal segments were superfused with saline solution containing papaverine to abolish contractile activity. Stepwise inflation of a balloon in which the cross-sectional area (CSA) was measured provided the luminal pressure-loading stimulus. The circumferential tension-strain relation was derived from steady-state values of internal radius and applied pressure. The intestinal weight, length, and weight per unit length increased significantly in untreated diabetic rats compared to the two other groups (P < 0.05). The body weight decreased in untreated diabetic rats compared to the two other groups (P < 0.05). The pressure-CSA relations differed between jejunum and distal ileum (P < 0.001) but not between the groups (P > 0.2). The tension-strain relations in jejunum and distal ileum were nonlinear and the curves for the two diabetic groups were shifted to the left compared to the curve for controls (P < 0.05), indicating increased wall stiffness. The histomorphometric data showed increased wall thickness in untreated diabetic rats compared to the two other groups both in jejunum and distal ileum (P < 0.02). Mucosal, submucosal, and muscle layer thicknesses did not differ between the three groups. No significant association was found between the histomorphometric and biomechanical parameters.