Bursting strength of syngeneic aortic vein grafts in the rat

Mechanical strength of the supradiaphragmatic part of the vena cava transplanted from one rat into the abdominal aorta of another rat of the same inbred strain was studied before transplantation, as well as 3 days and 1, 2, 3 and 4 weeks after transplantation. Bursting pressure was determined by distending the specimens with water at a constant infusion rate. The diameter of the specimens was measured at the moment of burst by a shadow technique, and the wall thickness by a micrometer on formalin-fixed and paraffin-embedded transverse sections, thus enabling calculation of bursting wall tangential and circular tension. No significant changes in bursting pressure were observed within 2 weeks after transplantation. Three and 4 weeks after transplantation a significant increase in bursting strength was observed. This increase coincided with the increase in collagen concentration previously reported. The previously reported initial decrease in collagen concentration did not, however, result in significant changes in the bursting strength. It is suggested that the increase in the thickness of the vein wall due to the increase of components other than collagen compensates for the loss of collagen.