Holstein T J, Fish W A, Stokes W M
J Lipid Res. 1966 Sep;7(5):634-8.
Suckling rats were killed at various intervals after intraperitoneal injection of acetate-1-(14)C and their brain sterols were analyzed by column, thin-layer, paper, and gas-liquid chromatography. The crude sterol (to which carrier zymosterol was added) was separated by column chromatography into cholesterol, desmosterol, and zymosterol fractions, and the specific activities of the recovered digitonides were determined. The zymosterol fraction, mainly carrier, was not uniformly labeled, in that the trailing half of the peak had a higher specific activity than the leading half. Evidence obtained suggests that this carbon activity was present in one or more sterols resembling zymosterol (Delta(8,24)-cholestadienol), Delta(7,24)-cholestadienol, and Delta(7,5.24)-cholestatrienol. The desmosterol and cholesterol were also carbon-labeled. The time course of the distribution of carbon activity among the above fractions indicated that the zymosterol fraction is a precursor of the desmosterol and that the desmosterol is, in turn, a precursor of the cholesterol. The data suggest that, in the developing brain of the rat, the course of the transformation of cholesterol precursors into cholesterol is influenced by the presence of at least two slow steps, one involving the conversion of Delta(7)- and Delta(8)-compounds to Delta(5)-compounds and the other, the reduction of the Delta(24)-unsaturation.
给乳鼠腹腔注射1-(14)C-乙酸盐后，在不同时间间隔将其处死，并通过柱色谱、薄层色谱、纸色谱和气液色谱分析其脑甾醇。将粗甾醇（加入了载体酵母甾醇）通过柱色谱分离为胆固醇、去氢胆固醇和酵母甾醇馏分，并测定回收的洋地黄皂苷的比活性。酵母甾醇馏分主要是载体，其标记不均匀，峰的后半部分比前半部分具有更高的比活性。获得的证据表明，这种碳活性存在于一种或多种类似于酵母甾醇（Δ(8,24)-胆甾二烯醇）、Δ(7,24)-胆甾二烯醇和Δ(7,5,24)-胆甾三烯醇的甾醇中。去氢胆固醇和胆固醇也被碳标记。上述馏分中碳活性分布的时间进程表明，酵母甾醇馏分是去氢胆固醇的前体，而去氢胆固醇又是胆固醇的前体。数据表明，在大鼠发育中的大脑中，胆固醇前体转化为胆固醇的过程受到至少两个缓慢步骤的影响，一个步骤涉及将Δ(7)-和Δ(8)-化合物转化为Δ(5)-化合物，另一个步骤是Δ(24)-不饱和键的还原。
