Max W. Biggs

Observations on the Fate of Ingested Cholesterol in Man

Tritium-labeled Cholesterol has been used to study several aspects of exogenous cholesterol metabolism in man. The rate and magnitude of the appearance of ingested cholesterol in the various blood compartments has been followed. Fecal excretion of the labeling material was measured. Cholesterol of dietary origin was demonstrated in a human atherosclerotic aorta.

Observations with Radioactive Hydrogen (H3) in Experimental Atherosclerosis

Tritium has been used to study certain aspects of endogenous and exogenous cholesterol metabolism in normal and hypercholesterolemic rabbits. Special attention is given to turnover studies on aortic cholesterol. Labeled cholesterol has been used for feeding experiments and the subsequent rise of serum cholesterol specific activity has been investigated.

Intestinal Lymphatic Transport of Absorbed Cholesterol.

Summary Exogenous cholesterol after its intestinal absorption was found to be conveyed into the systemic circulation by the lymph of the thoracic duct. Little or no transport occurred via the portal venous system.

Cholic acid and cholesterol: Studies concerning possible intraconversion

Abstract 1. 1. Tritium-labeled cholic acid was prepared by biosynthesis in the rat. 2. 2. The administration of tritium-labeled cholic acid to the bile duct obstructed rat followed by examination of the body cholesterol for activity gave no evidence of conversion of cholic acid to cholesterol. 3. 3. The conversion of cholesterol to cholic acid has been confirmed in the rat. 4. 4. The mechanism by which excess cholic acid produces excess hypercholesteremia in rats with biliary obstruction does not involve conversion of cholic acid to cholesterol.

Observations on Δ7-cholestenol metabolism in the rabbit☆

Abstract 1. 1. Tritium-labeled sterol appears in the free and total cholesterol pools of the serum of the rabbit following tritium-labeled Δ 7 -cholestenol feedings in a manner qualitatively similar to that occurring following tritiumlabeled cholesterol feedings. 2. 2. The conversion of Δ 7 -cholestenol to cholesterol has been demonstrated. Tritium-labeled cholesterol was isolated from the liver sterols of rabbits fed tritium-labeled Δ 7 -cholestenol.

A Quantitative Metabolic Defect in Lipid Metabolism Associated with Abnormal Serum Lipoproteins in Man

Tritium-labeled cholesterol has been fed to a selected series of patients to demonstrate a quantitative metabolic defect in lipid metabolism in the presence of abnormal serum lipoprotein spectra. Patients with abnormal serum lipoprotein spectra carry a greater fraction of their newly absorbed cholesterol in the esterified form than do normals.

The effect of Δ7-cholestenol feeding on the cholesterol and lipoproteins of rabbit serum.

Abstract 1. 1.When Δ 7 -cholestenol is fed to rabbits there is produced a rise in the various classes of low-density serum lipoproteins. The lipoprotein “pattern” is qualitatively the same as that observed after feeding cholesterol. 2. 2. Δ 7 -Cholestenol produces a striking rise in serum cholesterol, and about the same levels are reached as are observed on feeding cholesterol itself. The sterols of the serum after this feeding show a maximum of about 12% of Δ 7 -cholestenol. 3. 3. Δ 7 -Cholestenol and cholesterol produce an additive effect on the levels of serum lipoproteins when fed simultaneously. 4. 4. Five per cent of the serum sterols is Δ 7 -cholestenol at the end of 1 week of feeding both this sterol and cholesterol. At the end of 2 weeks the Δ 7 -cholestenol falls almost to zero in spite of continued feeding of both sterols.

OBSERVATIONS ON THE SUITABILITY OF TRITIUM-LABELED CHOLESTEROL FOR THE STUDY OF CHOLESTEROL METABOLISM

Abstract Following the feeding of cholesterol doubly labeled with radioactive hydrogen and carbon, the ratio of tritium specific activity to C14 specific activity in the serum cholesterol over a 10-day period was found to correspond to the ratio of tritium specific activity to C14 specific activity in the material fed. These results show that tritium-labeled cholesterol is a suitable tracer compound for biological investigations of many aspects of cholesterol absorption and turnover.