The saturated-fat-fed hamster as a model of atherosclerosis

Abstract

The need for an animal model o f atherosclerosis is fundamental to the processes of understanding and treating this all too common cause of death in the western world. Feeding animals with a cholesterol-supplemented diet has not proved to be a predicative model for drug treatment of atherosclerosis, but the arterial lesions produced by this technique have been shown to be similar to those found in man (Nistor et al., 1987). Spady & Dietschy (1988) have shown that feeding hamsters with a diet containing 20n% (w/w) coconut oil with a small supplement of cholesterol (0.1% w/w) produces a substantial hypercholesterolacmia. Deposition of cholesterol, as the ester, in the artery wall is presumably dependent on the action of acyl-CoA:cholestero1 acyltransfcrase (ACAT ). I t is possible that prolonged exposure o f the artery t o high plasma cholesterol levels causes an increase in ACAT activity in the artery wall. We have compared the effects of inducing hypercholesterolaemia by feeding hamsters with 20%) coconut oil in a diet already containing 0 . 1 % cholesterol with those found after feeding a diet supplementcd with 2% cholesterol. Plasma cholesterol. ACAT and 3-hydroxy-3-methylglutanyl (HMG)-CoA reductase activities in both liver and intestinal cells, and ACAT activity in thoracic aorta were measured after 1.2 and 4 weeks of feeding. Male Syrian hamsters weighing 100125 g at the start of the experiment were used, and weighed regularly throughout the experiment. After the animals had been fed on the diet for the required time, they were anaesthetized and the liver, intestine, aorta and a blood sample were taken for analysis. ACAT activity was assesed in liver microsomes and in homogenates of intestinal cells by measuring the incorporation of [ lJC]oleoyl coenzyme A into [ lJC]cholesteryl oleate as previously described (Suckling et a/., 1982). The aorta was prepared for assay by removing the adventitia and homogenizing the intimal layers in a Tris/HCI buffer with a glass/glass homogenizer. The homogenate was then incubated with [ “C]oleoyl coenzyme A and the [ “Clcholesteryl oleate formed was determined (our unpublished work). HMG-CoA reductase activity was quantified in liver microsomes and intestinal cell homogenates by the incorporation of [ ‘“C]HMG-CoA into [ 14C]mevalonic acid as previously described (Ingebritsen & Gibson, 1981). The products of these assays were separated from the substrate on silica t.1.c. plates, and quantified by scraping the appropriate peak of radioactivity for liquid scintillation counting. The plasma lipoproteins were fractionated by ultracentrifugation, and cholesterol concentrations in the fractions were determined