Aortic collagenase activity as affected by laparotomy, cecal resection, aortic mobilization, and aortotomy in rats

Recent biochemical evidence that aneurysm formation may be related to higher activated collagenase levels within aneurysmal aortic walls in association with reports of asymptomatic aneurysm rupture after laparotomy has led to speculation that operative trauma unrelated to direct aortic injury may increase the chance of aneurysm rupture by inducing collagenase activation within the aortic wall. The purpose of this study was to determine whether aortic collagenase can be activated by distant operative trauma and the kinetics of activation after injury. Ninety-six rats were divided into four groups: group 1--laparotomy alone; group 2--cecal resection; group 3--aortic mobilization; and group 4--aortotomy and repair. Animals within each group were sacrificed 1,3, and 6 hours and 1,2,3,4, and 5 days after surgery. The abdominal aortas were removed and assayed for collagenase activity by incubation with and digestion of tritium-labeled collagen. Collagenase activity was significantly elevated up to 6 hours after direct aortic injury (p less than 0.05) and decreased to normal levels within 2 days. Laparotomy, colon resection, and aortic mobilization had no significant effect on aortic collagenase activity compared to the controls. These data suggest that collagenase activity is a local phenomenon related to wound healing at the site of initial injury. Operative trauma without direct aortic injury had no effect on aortic collagenase activity.