A comparison of collagen levels in aorto-renal and aorto-intercostal atherosclerotic lesions in the cholesterol-fed rabbit

Collagen is the most abundant protein found in mammals. Its primary role is to give strength to structures such as bone, tendon and arteries. Collagen develops in atherosclerotic lesions after infiltration of the intima by lipids and monocytes. The authors have developed a video-microdensitometry method to measure, precisely, the collagen mass fraction in sections of atherosclerotic lesion. Four rabbits were fed a declining low level cholesterol diet for 6 months. Lesions were produced primarily to the sides and downstream from branch junctions. Collagen levels were measured in the periorificial lesion of the left aorto-renal and 3rd aorto-intercostal branch sites. Each lesion was sampled in three locations: immediately lateral to both sides of the branch orifice, downstream from the orifice and at the edge of the lesion. The renal values for the downstream, lateral and edge sites were 16.8±2.1 (SE)%, 16.7±1.1%, and 17.0±1.5% respectively, while the corresponding intercostal values were less for all sites, 12.58±0.85%, 14.5±1.3% and 10.67±0.72%. The edge and downstream sites were significantly different between branches (p<0.05 by individual t-tests). The lateral measurements were not shown to be different (p=0.30). These results suggest that collagen is laid down in different amounts according to its position along the artery wall. Physical factors such as local stress/strain distributions may influence collagen production in atherosclerotic lesions