Early Changes in Fine Structures of the Aortic Arch in Hamsters Fed a High Cholesterol Diet

Intimal changes at the prelesional stage of atherosclerotic lesions were investigated ultrastructurally using hamsters fed a high cholesterol diet for 1 day to 1 month. Observations were restricted to the lesionprone area in the aortic arch. The endothelial cells began to show well-developed rough endoplasmic reticulum and Golgi apparatus after a few days of the cholesterol diet. After three days, macrophages which contained a few lipid droplets were observed just below the endothelium. We found that the intimal smooth muscle cell formed a gap junction with the process of the medial smooth muscle cell. After a few weeks to 1 month on the diet, the intima became markedly thickened and filled with dense extracellular matrices. The intimal smooth muscle cells showed well-developed rough endoplasmic reticulum and Golgi apparatus with immature granules, suggestive of high secretory activity. The present study showed that endothelial ultrastructural changes, macrophage invasion, and medial smooth muscle cell migration are very early events occurring within a few days after cholesterol intake commences.