Free sterols of the cerebral white matter in experimental severe hypoxia

Wistar rats, aged 3.5 months, were subjected to severe hypoxia by placing them for 3 minutes in an atmosphere containing 2 kPa of oxygen. The myelin fraction was isolated from brains of the experimental animals at the following periods after the hypoxia event: 4 and 24 hours, 14 days, 2 months. The myelin neutral lipid extracts were fed into GC-MS system (gas chromatography-mass spectrometry) for identification of the separated free sterols. The free sterol spectrum of the myelin fraction of rats following the experimental hypoxia was variable unstable. The content of free cholesterol decreased and the contribution of minor sterols (24-ethylcholesterol, 24-ethyl-4-cholesten-3-on, 22-propyl-3 beta-hydroxy-5,24-cholestadien) changed. Lanosterol, one of the natural precursors in cholesterol biosynthesis happened to appear, and the content of the other precursor, desmosterol-increased. These changes may be indicative of some disturbances in the process of cholesterol biosynthesis induced by the experimental hypoxia. The occurrence of ethyl- and propylderivatives of cholesterol (compound found mainly in plant sterol spectra) in both the control and experimental myelin samples in either of the examined post-hypoxia periods is most likely the result of incorporation into myelin lipids of ingested plant sterols, nevertheless, endogenous synthesis cannot be ruled out.