Elastase and Collagenase Activities in the Wall of the Abdominal Aortic Aneurysm

Abstract

Some patients with arteriosclerosis of the abdominal aorta develop occlusive lesions (group O) while others develop aneurysmal dilatation (group A). Defects in the tissue organization, possibly secondary to a familial factor, are demonstrated by enzyme imbalance in the aortic wall.

The authors report their own experience in comparing elastase and collagenase activ ities between the two groups. Tissue from the aortic wall of 24 consecutive patients undergoing surgery for either aneurysmal (8 patients) or occlusive aortic disease (16 patients) was subjected to suitable biochemical assays. Four samples from group O were excluded because of low tissue weight and/or zero protein content. Aortic wall elastase was found to be significantly higher in group A than in group O. When expressed in nmol/gram tissue, the median elastase content in group A was 8.211 (range: 3.4078-14.2049) compared with 3.049 (range: 0-5.6359 of group O (P = 0.0030). This difference was still significant if it was expressed in nmol/gram protein, the comparable figures being 2.303 (range: 0.616-5.171) and 0.559 (0-1.345) respectively (P = 0.0018). On the other hand the authors were unable to confirm previous findings suggesting a variation in collagenase levels between the two groups either by using additive substrate (P = 0.3348) or by using endogenous substrate (P = 0.2170).

This suggest that collagenase may not be implicated in the development of aneurysmal dilatation. Alternatively it may be tightly bound or inhibited in the aortic tissue protein matrix in such a way as to make measurement of its activity difficult, while still contributing to the pathological process. More refined techniques of detecting colla genase may therefore be required.