Patterns of Sudanophilic Lesions at Ostia of Descending Thoracic and Abdominal Aorta in Cholesterol-Fed Adult Rabbits

sudan-positive atherosclerotic lesions preferentially occur at downstream and lateral margins of arterial branch ostia in human neonates and weanling rabbits but tend to develop at lateral and upstream margins in old subjects. we investigated (i) the pattern of sudanophilic lesions at aortic ostia of cholesterol-fed adult rabbits and (ii) determined any differences in lesion distribution between descending thoracic and abdominal aorta. ten adult males, new zealand white rabbits were fed 2% high cholesterol diet. after six weeks, aortas were excised, opened longitudinally and stained with sudan-iv for gross examination of atherosclerotic lesions. a total of 156 descending thoracic and 90 abdominal ostia were examined. mean lesion frequencies upstream, downstream and at lateral margins of the affected ostia were calculated and compared. sudanophilic lesions were detected around 32% ostia of descending thoracic aorta and 25% those of abdominal aorta. at ostia of descending thoracic aorta, lesion frequencies were significantly higher (p<0.001) downstream (95%) and at lateral margins (92%) than upstream (2%). in abdominal aorta, lateral (100%) and upstream (43%) margins were significantly (p<0.05) more affected while minimal lesion frequencies were seen at downstream branch points (9%). comparison between descending thoracic and abdominal aorta showed an insignificant difference of lesion frequencies at lateral margins (p>0.05) but a highly significant difference at upstream versus downstream of ostia (p<0.001). we concluded that in cholesterol-fed adult rabbits, juvenile pattern of downstream lipid deposition persists at ostia of descending thoracic aorta while a switch towards the upstream pattern of old subjects occurs at ostia of abdominal aorta.