Three-dimensional architecture of elastic tissue in early atherosclerotic lesions of the rat aorta.

The overall three-dimensional architecture of elastic tissue in early atherosclerotic lesions of the rat aorta was studied using scanning electron microscopy (SEM) after hot-formic acid extraction followed by a freeze-drying method. These lesions were induced by feeding the rats a diet containing 2% cholesterol, 0.5% cholic acid and 0.2% methylthiouracil. SEM revealed two types of alterations in the elastic tissue; one was an increase in the dome-like elastic lamina with few fenestrations that might be due to the reduplication of the internal elastic lamina (IEL), and the other was an increase in fibrous elastin, generally oriented longitudinally in the intima. The former was discussed with respect to its barrier function to such macromolecules as fibrinogen and low density lipoprotein (LDL), and was assumed to be a structure related to prevention of early atherosclerotic lesions.