Persistence of Sterols other than Cholesterol in Chicken Tissues

Abstract

RECENT work by Davison and his collaborators^1–3 has shown that cholesterol may be incorporated in the nervous tissues of myelinating chickens and rabbits and that this cholesterol will persist in these tissues for considerable lengths of time. Our interests in the metabolism of cholesterol and other sterols prompted us to compare the distributions in chicken tissues of injected sitosterol and lanosterol with that of cholesterol. Emulsions of cholesterol-7-³H (purchased from New England Nuclear Co., Boston, Mass.), sitosterol³-H (randomly labelled, gift of Dr. Leon Swell), and lanosterol-³H (randomly labelled, gift of Dr. George J. Alexander) in saline were prepared by the method used for preparation of cholesterol-¹⁴C emulsions for experiments involving mitochondrial oxidation of this sterol⁴. Newly hatched White Leghorn chicks were used and the appropriate sterol emulsion (0.50 ml.) was injected directly into the yolk sac. After four days, radioactivity could be detected in the brain tissue of chickens from each group. After 9 weeks the one surviving chicken in each group was killed by exsanguination. The blood was collected in centrifuge tubes and the erythrocytes separated. All the brain, cord, liver, spleen and aorta was excised, weighed and dissolved in strong potassium hydroxide. The non-saponifiable fraction was assayed for tritium radioactivity in a liquid scintillation counter. Small pieces of sciatic nerve were taken from each chicken and all showed slight but consistently detectable radioactivity. Other findings are shown in Table 1.