Nes W R, Adler J H, Billheimer J T, Erickson K A, Joseph J M, Landrey J R, Marcaccio-Joseph R, Ritter K S, Conner R L
Lipids. 1982 Mar;17(3):257-62. doi: 10.1007/BF02535113.
The delta 5-sterol, androst-5-en-3 beta-ol, which has no side chain at C-17, did not permit molting of the insect Heliothis zea, growth of either the protozoan Tetrahymena pyriformis, or the yeast Saccharomyces cerevisiae adapted to anaerobic conditions, nor was the sterol esterified by a mammalian microsomal ACAT preparation. However, the sterol did form a liposome with egg lecithin and, when fed to mice, did inhibit hepatic cholesterol synthesis. 21-Isopentylcholesterol also formed a liposome but neither supported the growth of the yeast nor was metabolized by the protozoan. When sterols, 20(R)-n-alkylpregn-5-en-3 beta-ols, with side chains of varying lengths were added to the medium of the protozoan, maximal esterification with fatty acids occurred with the 20(R)-n-pentyl derivative, and maximal inhibition of tetrahymanol formation occurred with the n-butyl, n-pentyl, and n-hexyl derivatives. In all of the assays cholesterol showed a positive response, either permitting molting or growth, being metabolized, inhibiting sterol or tetrahymanol synthesis, or forming a liposome.
Δ5-甾醇，雄甾-5-烯-3β-醇，在C-17位没有侧链，它既不能使昆虫烟芽夜蛾蜕皮，也不能支持梨形四膜虫原生动物或适应厌氧条件的酿酒酵母生长，并且该甾醇也不能被哺乳动物微粒体ACAT制剂酯化。然而，该甾醇确实能与鸡蛋卵磷脂形成脂质体，并且当喂给小鼠时，确实能抑制肝脏胆固醇的合成。21-异戊基胆固醇也能形成脂质体，但既不支持酵母生长，也不被原生动物代谢。当将具有不同长度侧链的甾醇20(R)-正烷基孕甾-5-烯-3β-醇添加到原生动物培养基中时，20(R)-正戊基衍生物与脂肪酸的酯化作用最强，而正丁基、正戊基和正己基衍生物对四膜虫醇形成的抑制作用最强。在所有试验中，胆固醇都表现出阳性反应，要么允许蜕皮或生长，被代谢，抑制甾醇或四膜虫醇合成，要么形成脂质体。
