正常血圧ならびに高血圧ウサギにおける動脈硬化症の進展と退縮

―画像解析装置による冠状動脈病変の定量的分析―

抄録

Regression of coronary atherosclerosis has been reported in dogs and monkeys, but minimal or no regression was noted in chickens and rabbits. These conflicting results probably derived not only from animal species chosen, but also from differences of experimental period or methods of analysis. In the present study we attempted to quantitate sequential changes of rabbit's coronary atherosclerosis with an aid of the image processing system.
Normotensive and hypertensive rabbits were placed on a 0.5% cholesterol diet for 16 weeks and observed up to 60 weeks. Prior to cholesterol feeding constriction of bilateral renal arteries were performed in the latter group and established hypertension with systolic pressure of 150mmHg or over. The left coronary artery of every 2.5mm was dissected transversely up to ten segments. Histometric quantitative analysis was carried out concerning the luminal diameter of the arterial segments and degrees of luminal stenosis of arteries in cross-sectional area.
In normotensive rabbits coronary lesions had a predilection to localize in the proximal subepicardial portion and the bifurcation of intramural arteries. Hypertensive rabbits exhibited more extensive and accentuated coronary lesions not only in the subepicardial but also in the intramural portions of the artery with marked fibromuscular proliferation and foam cell infiltration. Advanced sclerotic lesions such as atheroma or calcification occurred after 28 weeks in a half of normotensive and two thirds of hypertensive animals. One normotensive and two hypertensive rabbits revealed myocardial infarction at 16 and 28 weeks. After cessation of cholesterol feeding disappearance of foam cells and attenuation of connective tissue matrices were noted in contrast to further fibromuscular proliferation. Significant reduction of accentuated coronary lesions with luminal narrowing of more than 50% were observed in both normotensive and hypertensive animals sacrified after 40 and 60 weeks.
In conclusion, the present study indicates that coronary lesions of both normotensive and hypertensive rabbits have a tendency to regress more easily than aortic atherosclerotic lesions which we have previously reported. This dissociation of reversibility between two vascular systems probably derives from differences of nature of the foregoing intimal changes, susceptibility to atherogenic promoting factors, or erects of hypertension on the vascular wall.