INCREASED TURNOVER OF COLLAGEN IN ABDOMINAL AORTIC-ANEURYSMS, DEMONSTRATED BY MEASURING THE CONCENTRATION OF THE AMINOTERMINAL PROPEPTIDE OF TYPE-III PROCOLLAGEN IN PERIPHERAL AND AORTIC BLOOD-SAMPLES

Purpose: The pathogenesis of abdominal aortic aneurysm (AAA) involves many factors; elastin degradation is believed to lead to initial dilat ion, whereas changes in the collagen structure predispose the aneurysm to rupture. The major collagens in the aortic wall are types I and II I. We set out here to determine whether changes in serum propeptide of type III procollagen (PIIINP), a biologically relevant marker of type III collagen turnover, could be associated with the characteristics o f AAA. Methods: The aminoterminal PIIINP and the carboxyterminal prope ptide of type I collagen were measured by radioimmunoassay in 87 patie nts with AAA and 90 control subjects with aortodistal arteriosclerosis . The Samples were taken from the peripheral blood and from the abdomi nal aorta at the levels of the diaphragm and the common iliac artery. Results: Mean PIIINP concentrations were higher in patients with AAA t han in control subjects (3.47 mu g/L vs 2.73 mu g/L, P < 0.0001), corr elating positively with aneurysm diameter in the former (r = 0.27, P = 0.04) and with the maximum thickness of the intraluminal thrombus (r = 0.39, p = 0.003). The gradient in PIIINP between the upper and lower end of the abdominal aorta was significant in the AAA group (- 0.30 m u g/L, range - 0.20 to -0.50 vs - 0.10 mu g/L, range -0.20 to 0.30, p = 0.002). Conclusions: These studies indicate that the turnover of typ e III collagen is increased in patients with AAA.