THE BIOSYNTHESIS OF CHOLESTEROL AND OTHER STEROLS BY BRAIN TISSUE |
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Authors: | R. B. Ramsey J. P. Jones A. Rios H. J. Nicholas |
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Affiliation: | Institute of Medical Education and Research, and Department of Biochemistry, St. Louis University School of Medicine, St. Louis, Missouri 63104 |
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Abstract: | Abstract— The distribution of [14C]-labeIled material into subcellular fractions of 15-day-old rat brain was studied as a function of time after intracerebral injection of [2-14C]mevalonic acid. As previously shown for adult brain, the data indicated the microsomal fraction to be the site of sterol biosynthesis. The synaptosomal fraction exhibited a marked early uptake of [14C]-nonsaponifiable material. Total radioactivity in both myelin and myelin-like fractions remained low in comparison to that in the other subcellular fractions at all time periods examined. At 2 h after injection, labelled digitonin-precipitable material was demonstrable in all subcellular fractions. Examination of the [14C]-labelled nonsaponifiable material by thin-layer chromatography indicated the rapid appearance of labelled 4-desmethyl sterol in all subcellular fractions, with the most rapid appearance in the myelin fraction, followed in decreasing order by microsomal, synaptosomal, and mitochondrial fractions. Examination of [14C] digitonin-precipitable material from each fraction by the dibromide method demonstrated that although 4-desmethyl sterol appeared quickly, the formation of cholesterol was slow in all fractions, an effect that had been reported earlier for adult brain. |
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