Morphologic Changes in the Aorta during Elastase Infusion in the Rat Aneurysm Model

Background. The morphologic changes in the aorta during elastase infusion, which have not previously been investigated, were examined in the rat abdominal aortic aneurysm model. Materials and Methods. A total of 80 Wistar rats were divided into five groups. A 1.0-cm segment of infra-renal abdominal aorta was infused with 25 U of elastase in 1 mL saline for 10 (n = 14), 20 (n = 14), 30 (n = 14), 60 (n = 19), or 120 min (n = 19). In the 120-min group, transparency and aortic diameter were recorded every 10 min. In each group, 7 rats were killed immediately after infusion. The aortas were excised for histologic examination. The aortic diameters were measured 7 days after infusion in the remaining rats. Results. The infused aorta became transparent within 50 min of elastase infusion. The aortic diameter increased rapidly for the first 30 min of infusion. Histologically, the elastic tissue was completely absent after 60 min of infusion. The aortic diameters in the 60- and 120-min groups were not significantly different 7 days after infusion. Conclusions. Morphologic changes in the infused aorta are complete after 60 min of elastase infusion. It may be possible to shorten the elastase infusion time from 120 to 60 min in this model.