Increased amount of type III pN-collagen in AAA when compared with AOD

Objective. the extent of the processing of type III procollagen to type III Collagen was determined in nine human abdominal aortic aneurysms (AAA), and compared with ten samples of aortoiliac occlusive disease (AOD). Methods: the aminoterminal propeptide (PIIINP) and telopeptide (IIINTP) of type III procollagen and collagen, respectively, were immunologically measured in the soluble and insoluble fractions of the extracellular matrix, The assay for PIIINP in the insoluble matrix was further validated. Results: the insoluble matrices of AAAs contained at least 12 times more incompletely processed type III pN-collagen than AOD specimens (0.74% and 0.061%, respectively). Also, the soluble extracts of AAAs; tended to contain more nonprocessed type III pN-collagen than free, properly cleaved aminoterminal propeptide. Conclusions. the larger amount of type III pN-collagen suggests an alteration in the metabolism of type III collagen in AAAs. This may partially explain the decreased tensile strength of the aortic tissue.