Adherent leukocytes to the aortic wall promotes atherosclerosis in the Watanabe heritable hyperlipidemic rabbits

It is well known that leukocytes adherence to the endothelium of arterial wall occurs in diet-induced hypercholesterolemic animals. We examined the relationship between leukocytes adherence and atherosclerosis in the thoratic aorta of the Watanabe heritable hyperlipidemic rabbits (WHHL rabbits). Five of 2 or 3 months old WHHL rabbits were sacrificed and after perfusion fixation with 2.5% gulutaraldehyde, thoratic aorta was taken out carefully and divided into the 4 portions: Portion 1; cranial side of aortic arch, Portion 2; caudal side of aortic arch, Portion 3; upper side of thoratic aorta except aortic arch, Portion 4; lower side of thoratic aorta except aortic arch. Three to 6 samples from each portion except branching sites were examined using electron microscopy, and the counts of adherent leukocytes (LC) in each portion were calculated. Seven of 6 to 12 months old WHHL rabbits were sacrificed and the internal side of thoratic aorta was cut opened from the ventral side and the atherosclerotic lesions were copied. From these copies, the % area of atherosclerotic plaques (%AT) in each 4 portions as described was calculated using microcomputer. LC in Portion 1 to 4 was 265 +/- 62, 234 +/- 46, 53 +/- 8 and 41 +/- 13/mm2 respectively. LC in Portion 1 or 2 was significantly larger than that in Portion 3 or 4 (p < 0.05). The endothelium to which leukocytes adhered was intact. %AT in Portion 1 to 4 was 68 +/- 8, 63 +/- 8, 40 +/- 8 and 34 +/- 8% respectively. %AT in Portion 1 or 2 was significantly larger than that in Portion 3 or 4 (p < 0.05). It is concluded that leukocytes adherence to the intact endothelium of the arterial wall was one of the geneses and promoters of atherosclerosis in WHHL rabbits.