Biomechanical properties of the rat oesophagus in experimental type-1 diabetes

The gastrointestinal tract remodels its morphology and circumferential stress-strain properties in diabetes mellitus. This study adds one more piece of mechanical knowledge, namely the oesophageal shear modulus and its dependence on the circumferential and longitudinal stresses and strains of oesophagus in diabetic rats and control rats. Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg kg(-1) body weight). The diabetic rats lived up to 28 days after the induction of diabetes. The oesophagus was studied in vitro using a triaxial machine. Stepwise elongation and inflation plus continuous twist were carried out with measurement of the resultant forces. Circumferential and longitudinal stresses and strains were computed from steady-state values of longitudinal force, outer diameter and the applied pressure. The shear modulus was computed from the twist angle-torque relationship. The circumferential and longitudinal stress-strain relationships were exponential. The circumferential stiffness increased 1 week after induction of diabetes (P < 0.001). The longitudinal stiffness increased in the 4-week diabetic rats (P < 0.001). The shear modulus varied as function of longitudinal strain and pressure. The oesophagus became stiffer in shear 4 weeks after the induction of diabetes (P < 0.001).