title: Digitonide precipitable sterols: a reevaluation with special attention to lanosterol.
abstract: The ability of digitonin to precipitate lanosterol from prepared mixtures and biological sources was evaluated. Commercially available lanosterol was determined to be composed of about 60% lanosterol and 40% dihydrolanosterol. Both sterols were only partially precipitated by digitonin under all conditions examined. The presence of cholesterol increased the precipitation of lanosterol, but never to completion. About 40% of the lanosterols from saponified sheep's-wool fat was not precipitated by digitonin. Also 14C-labeled lanosterol recovered from rat brain following intracerebral injection of 2-[14C]mevalonate was only 70% precipitated by digitonin. Steric hinderance by the methyl groups at carbon -4 is suggested to explain the poor precipitability of this sterol. In conclusion, lanosterol can not be considered to be a digitonide-precipitable sterol equivalent to cholesterol. Caution should be exercised in situations where digitonin-precipitable sterols are being prepared from sources containing significant concentrations of lanosterol (i.e., mass and/or radiolabel).
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002250:Carbon Radioisotopes; D004072:Digitonin; D007810:Lanosterol / Q000302:isolation & purification*; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D012756:Sheep; D013261:Sterols / Q000302:isolation & purification*; D013329:Structure-Activity Relationship; D014935:Wool
chemical_list: D002250:Carbon Radioisotopes; D013261:Sterols; D007810:Lanosterol; D004072:Digitonin