ELASTIN IS INCREASED IN ABDOMINAL AORTIC-ANEURYSMS

The decrease in elastin concentration in abdominal aortic aneurysm (AA A) has been ascribed to elastolysis. The discordant response of the el astin and collagen genes in AAA suggests a different explanation: dilu tion of elastin because of higher levels of synthesis of collagen and other matrix proteins. The purpose of this study was to determine circ umferential content of elastin, collagen, and total protein in aneurys mal (AAA), atherosclerotic, and normal (NL) infrarenal aorta. Standard serial extraction techniques of complete 1-cm rings of midinfrarenal aortic tissue were used to remove soluble protein, calcium, and lipids . Hydroxyproline (collagen), desmosine/isodesmosine (elastin), and tot al amino acid (total protein) content were determined by amino acid an alysis. Means values (+/-SEM) were compared by ANOVA. Circumferential content of desmosine/isodesmosine was increased 2.5-fold in AAA compar ed to NL (P < 0.05). Collagen and total protein were increased 5.7- an d 4.7-fold, respectively (P < 0.05). There was a high degree of correl ation between circumference and collagen content (r = 0.89). These dat a demonstrate that significant synthesis of matrix proteins accompanie s aortic dilatation. While both elastin and collagen are increased, th ere is a much greater increase in circumferential collagen content tha n elastin content. These data do not preclude proteolysis as a factor in AAA but suggest that the decrease in elastin concentration results from dilution of elastin by a greater increase in the synthesis of oth er matrix proteins and that synthesis is an important factor in AAA fo rmation. (C) 1994 Academic Press, Inc.