title: Novel LC-MS/MS method for assay of 7alpha-hydroxy-4-cholesten-3-one in human plasma. Evidence for a significant extrahepatic metabolism.
abstract: A new isotope dilution LC-MS/MS method for assay of 7alpha-hydroxy-4-cholesten-3-one without need for derivatization is described. This method was used in catheterization experiments on healthy fasting volunteers. The levels of this generally used marker for bile acid synthesis were slightly but significantly higher in the hepatic vein than in the brachial artery. In contrast, the levels of the precursor to 7alpha-hydroxy-4 cholesten-3-one, 7alpha-hydroxycholesterol, were the same in the two vessels. It is concluded that there is a net extrahepatic metabolism of 7alpha-hydroxy-4-cholesten-3-one. The similarity and very high correlation between the levels in the two vessels (r=0.97) are consistent with the contention that 7alpha-hydroxy-4-cholesten-3-one is a suitable marker for the activity of the hepatic cholesterol 7alpha-hydroxylase and thus bile acid synthesis.
authors.affiliation: Division of Clinical Chemistry, Karolinska University Hospital, Huddinge and Solna, Sweden.
authors.forename: Anita
authors.initials: A
authors.lastname: Lövgren-Sandblom
authors.forename: Maura
authors.initials: M
authors.lastname: Heverin
authors.forename: Hanna
authors.initials: H
authors.lastname: Larsson
authors.forename: Eija
authors.initials: E
authors.lastname: Lundström
authors.forename: John
authors.initials: J
authors.lastname: Wahren
authors.forename: Ulf
authors.initials: U
authors.lastname: Diczfalusy
authors.forename: Ingemar
authors.initials: I
authors.lastname: Björkhem
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D053719:Tandem Mass Spectrometry / Q000379:methods*