Fatty streak initiation in Watanabe Heritable Hyperlipemic and comparably hypercholesterolemic fat-fed rabbits.

Morphologic and immunocytochemical studies were conducted to determine the sequence of cellular interactions that occur during the initiation of the fatty streak in the aorta of Watanabe Heritable Hyperlipemic rabbits and comparably hypercholesterolemic fat-fed rabbits. Watanabe rabbits from 3.5 weeks gestation to 2 months of age and fat-fed rabbits from 1 week to 2 months duration of hypercholesterolemia were compared utilizing light microscopic and scanning and transmission microscopic techniques. In both groups of animals, the earliest detectable events were an increase in monocyte adherence and subendothelial migration followed by formation of a single layer of intimal macrophage-derived foam cells. Immunocytochemical studies using macrophage-specific and muscle-actin-specific monoclonal antibodies support the morphologic data which suggests that the early fatty streak in both the Watanabe and fat-fed rabbits is predominantly composed of macrophage-derived foam cells. Thus, the absence of functional low density lipoprotein receptors in the Watanabe rabbit and differences in the distribution of cholesterol among the lipoproteins in the Watanabe and fat-fed rabbits do not appear to alter the initial responses of the cells of the artery wall to chronic hypercholesterolemia.