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In guinea pigs fed a diet enriched with 1% cholesterol, the liver, adrenals, spleen, and small intestine accumulated cholesterol much more than the lungs and kidneys. The cholesterol content of the aorta, stomach and colon was not increased by the diet. Cholesteryl ester was the predominant form of cholesterol deposited in the organs richest in this sterol and the total cholesterol content of a tissue tended to increase with the proportion of cholesteryl ester. Cholesterol esterifying activity (ACAT) was found in most tissues and paralleled the cholesteryl ester content of these tissues, being highest in the adrenals, liver, spleen and the proximal part of the small intestine. ACAT activity was enhanced by the cholesterol diet and its elevation was fairly well correlated with the increase in the cholesterol content of the organs. However, the liver and adrenals tended to accumulate more cholesterol than anticipated from their cholesteryl ester content and their ACAT activity. Cholesterol esterification may play a major role in the ability of organs to accumulate cholesterol.

In various organs of the guinea pig, the total cholesterol content of an organ was significantly correlated with the percentage of esterified cholesterol present in this organ. Cholesterol esterifying capacity was shown in most organs, with highest activities in the adrenals, the spleen and the liver. The significant correlation found between the cholesteryl ester content of an organ and its acyl cholesterol acyltransferase activity suggests a possible role of this enzyme in determining the level of the total and esterified cholesterol in a tissue.