Abstract
The aortic wall structure of genetically determined hypercholesterolaemic (Yoshida) and control (Brown-Norway) rats was investigated by transmission and scanning electron and light microscopy. Leucocyte adherence mostly at branch sites and irregular protrusive structures were observed on the endothelial surface of the thoracic aorta of Yoshida, but not of Brown-Norway rats. The subendothelial space of the aortic wall of Yoshida rats was characterized by intimal cushions consisting of smooth muscle cells of 'synthetic phenotype' associated with adhering leucocytes and lipid droplets. Lipid infiltration of the cytoplasm of medial smooth muscle cells was observed on the inner part of the aortic arch and on the lateral parts of the large branches of Yoshida rats. This model of spontaneously hyperlipidaemic Yoshida rats is an appropriate 'moderate' injury system, which may be useful for studies of multiple risk factors for atherogenesis.