Abstract
Controversy exists as to whether atherosclerotic lesions were reversible or not. These conflicting views mainly derived from differences of animal species, experimental designs, or methods of evaluation. In the present study we attempted to quantitate sequential changes of sclerotic lesions with an aid of the image processing system.
Normotensive and renovascular-hypertensive rabbits were placed on a 0.5% cholesterol diet for 16 weeks and observed up to 120 weeks. After measuring surface involvement (SI) by the point counting method, a representative longitudinal section covering the whole length of the aorta was obtained, and histometric quantitative analysis was carried out concerning foam cell infiltration, fibromuscular proliferation, and atheroma formation. In addition, 10 continuous step sections of the left coronary artery (and its branches) was prepared, and the degrees of luminal stenosis were estimated in all arterial segments contained in the sections.
After stopping of cholesterol feeding, foam cell lesion of the aorta and coronary artery was gradually replaced by fibromuscular tissue. A greater degree of smooth muscle cell proliferation was a feature of hypertensive animals. Formation of atheroma occurred almost invariably after 12 weeks return to the normal diet. It was noted that hypertension accentuated the severity and extent of both aortic and coronary lesions.
Evidence of regression of nonatheromatous as well as atheromatous lesions was obtained in normotensive rabbits (and partially in hypertensive rabbits) sacrificed after 44 weeks return to the normal diet. Significant reduction of coronary lesions with luminal narrowing of more than 60 % were also documented in both normotensive and hypertensive animals. In conclusion, the present study indicated that, even in the hypertensive animals, regression of both aortic and coronary lesions of the rabbits could occur following a long period of dietary manipulations. The extent of regression, however, appeared to be less prominent, when compared with several observations demonstrated in monkeys.
