Cholesterol oxidation products (oxysterols) have been detected in many different tissues, often at concentrations 10 to 10 times lower than cholesterol. This constitutes a considerable risk of quantitation errors, since even a minor oxidation of cholesterol during sample processing would yield a substantial increase of oxysterol levels. It has therefore been suggested that some of the oxysterols do not occur in vivo and their detection in tissues merely are artifacts produced in vitro.

In the present work, an O inhalation technique was developed in order to clarify which oxysterols are produced in vivo. Rats were exposed for 3 h to an atmosphere with a composition similar to normal air, except that it contained O instead of O. Control rats were kept in O-containing atmosphere throughout the experiment. The O enrichment of oxysterols in plasma and liver was determined by gas/liquid chromatography-mass spectrometry and mass isotopomer distribution analysis.

In vivo formation of oxysterols, indicated by enrichment in O, was established for cholest-5-ene-3,7-diol, cholest-5-ene-3,7-diol, 7-oxocholesterol, cholest-5-ene-3,24-diol, cholest-5-ene-3,25-diol, and cholest-5-ene-3,27-diol. Additionally, it seems likely that cholest-5-ene-3,4-diol is formed in vivo. The O labeling pattern suggests that there is incomplete equilibration between the liver and plasma pools of cholest-5-ene-3,27-diol. No evidence for the in vivo formation of 5,6-oxygenated oxysterols was obtained.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				J. Linseisen, G. Wolfram, and A. B. Miller Plasma 7{beta}-Hydroxycholesterol as a Possible Predictor of Lung Cancer Risk Cancer Epidemiol. Biomarkers Prev., December 1, 2002; 11(12): 1630 - 1637. [Abstract] [Full Text] [PDF]

				D. Lutjohann, A. Brzezinka, E. Barth, D. Abramowski, M. Staufenbiel, K. von Bergmann, K. Beyreuther, G. Multhaup, and T. A. Bayer Profile of cholesterol-related sterols in aged amyloid precursor protein transgenic mouse brain J. Lipid Res., July 1, 2002; 43(7): 1078 - 1085. [Abstract] [Full Text] [PDF]

				I. Bjorkhem and U. Diczfalusy Oxysterols: Friends, Foes, or Just Fellow Passengers? Arterioscler. Thromb. Vasc. Biol., May 1, 2002; 22(5): 734 - 742. [Abstract] [Full Text] [PDF]

				J. Plat, H. Brzezinka, D. Lutjohann, R. P. Mensink, and K. von Bergmann Oxidized plant sterols in human serum and lipid infusions as measured by combined gas-liquid chromatography-mass spectrometry J. Lipid Res., December 1, 2001; 42(12): 2030 - 2038. [Abstract] [Full Text] [PDF]

				S. Meaney, M. Hassan, A. Sakinis, D. Lütjohann, K. von Bergmann, A. Wennmalm, U. Diczfalusy, and I. Björkhem Evidence that the major oxysterols in human circulation originate from distinct pools of cholesterol: a stable isotope study J. Lipid Res., January 1, 2001; 42(1): 70 - 78. [Abstract] [Full Text]

				H. N. Hodis, S. Hashimoto, W. J. Mack, and A. Sevanian Probucol Reduces Oxysterol Formation in Hypertensive Rabbits Hypertension, September 1, 2000; 36(3): 436 - 441. [Abstract] [Full Text] [PDF]

				G. J. Schroepfer Jr. Oxysterols: Modulators of Cholesterol Metabolism and Other Processes Physiol Rev, January 1, 2000; 80(1): 361 - 554. [Abstract] [Full Text] [PDF]

				I. Staprans, X.-M. Pan, J. H. Rapp, and K. R. Feingold Oxidized Cholesterol in the Diet Accelerates the Development of Aortic Atherosclerosis in Cholesterol-Fed Rabbits Arterioscler. Thromb. Vasc. Biol., June 1, 1998; 18(6): 977 - 983. [Abstract] [Full Text] [PDF]

				I. Bjorkhem, D. Lutjohann, O. Breuer, A. Sakinis, and A. Wennmalm Importance of a Novel Oxidative Mechanism for Elimination of Brain Cholesterol. TURNOVER OF CHOLESTEROL AND 24(S)-HYDROXYCHOLESTEROL IN RAT BRAIN AS MEASURED WITH 18O2 TECHNIQUES IN VIVO AND IN VITRO J. Biol. Chem., November 28, 1997; 272(48): 30178 - 30184. [Abstract] [Full Text] [PDF]

				D. S. Lala, P. M. Syka, S. B. Lazarchik, D. J. Mangelsdorf, K. L. Parker, and R. A. Heyman Activation of the orphan nuclear receptor steroidogenic factor 1 by oxysterols PNAS, May 13, 1997; 94(10): 4895 - 4900. [Abstract] [Full Text] [PDF]

				J. T. Salonen, K. Nyyssonen, R. Salonen, E. Porkkala-Sarataho, T.-P. Tuomainen, U. Diczfalusy, and I. Bjorkhem Lipoprotein Oxidation and Progression of Carotid Atherosclerosis Circulation, February 18, 1997; 95(4): 840 - 845. [Abstract] [Full Text]