Stable isotope methodology for kinetic studies of interconversion of cortisol and cortisone in a human subject

Oral administration of 5 mg each of deuterium-labeled cortisol ([1,1,19,19,19-H-2(5)]cortisol, cortisol-d(5)) and cortisone-d(5) ([1,1,19,19,19-H-2(5)]cortisone) to a human subject on two different occasions four weeks apart provided a useful means of characterizing the kinetics of the interconversion of cortisol and cortisone. From the data on plasma concentration measurements of cortisol-d(5), cortisone-d(5), endogenous cortisol and endogenous cortisone by gas chromatography-mass spectrometry, it was demonstrated that (I) the plasma concentration ratio of cortisone-d(5) to cortisol-d(5) approached a plateau 4-5 h following either the cortisol-d(5) or cortisone-d(5) administration and the plateau values for the cortisone-d(5) and cortisol-d(5) administration were almost identical (about 0.43) and (2) dosing with only 5 mg of the deuterium-labeled steroids suppressed the plasma concentrations of endogenous cortisol and cortisone. (C) 1998 by Elsevier Science Inc.