Spontaneous lesions in the rat caudal artery. Effects of diet-induced hypercholesterolaemia alone and in association with hypertension.

Caudal arterial lesions form spontaneously with age in the male Wistar rat and are characterized by a break in the internal elastic lamina (IEL), with associated damage to endothelium and underlying smooth muscle cells followed by rapid repair. Such lesions have been studied under conditions of hypercholesterolaemia. Diet-induced hypercholesterolaemia did not enhance the formation of these lesions compared to age-matched control rats. Lesioned areas of caudal arteries from hypercholesterolaemic rats showed marked or slight focal lipid deposits depending upon their location along the artery. Studies in rats of different ages suggest that the majority of lipid probably accumulates during the phase of lesion repair and that the absence of the IEL per se does not appear to be responsible for the lipid accumulation. The effect of hypertension associated with hypercholesterolaemia on caudal arterial lesions was studied using DOCA salt-Wistar and spontaneously hypertensive rats. The association of these two factors did not increase lesions either in the caudal artery or in the renal artery studied for comparison. In caudal artery the number of fatty lesions appeared to be related more to the level of cholesterolaemia than to blood pressure. The extent of lipid accumulation within lesions in the caudal artery appears not to correlate with that in the renal artery, demonstrating the importance of local factors.