Detection of monohydroxy "bile" acids in the brains of guinea pigs afflicted with experimental allergic encephalomyelitis.

3alpha-Hydroxy-5-cholanoic acid (lithocholic acid) and some unidentified acids (one of them perhaps 3-hydroxy-cholest-5-en-26-oic acid) have been detected in the brains of guinea pigs afflicted with experimental "allergic" encephalomyelitis. None of the acids could be identified in comparable amounts of brain tissue from normal guinea pigs. Thin-layer chromatography of the free acids, and thin-layer and gas-liquid chromatography combined with mass spectrometry of the methyl esters were used for identification. The occurrence of these acids may possibly be the result of cholesterol oxidation in the brain. The acids, or compounds related to them, may play a role in development of demyelination in experimental allergic encephalomyelitis.