Evaluation of 11beta-HSD activities in vivo following oral administration of cortisol-13C4,2H1 to a human subject.

This study is concerned with an oral administration of 5mg of [1,2,4,19-13C(4),11alpha-2H]cortisol (cortisol-13C(4),2H(1)) to a human subject to reliably evaluate the individual activities of two isozymes of 11beta-HSD. The use of a GC-MS method allowed the simultaneous measurement of the plasma concentrations of cortisol-13C(4),2H(1), cortisone-13C(4), and cortisol-13C(4) together with endogenous cortisol and cortisone. The loss of 11alpha-2H during the conversion of cortisol-13C(4),2H(1) to cortisone-13C(4) by 11beta-HSD2 and the regenerated cortisol-13C(4) from cortisone-13C(4) by 11beta-HSD1 provided a direct and accurate means of distinguishing the activities of the two isozymes. The kinetic analysis associated with the metabolism of orally administered cortisol-13C(4),2H(1) was of great importance in assessing the 11beta-HSD activities. From a viewpoint of the chemical stability and much less pronounced kinetic isotope effect of the 13C-label and the 2H-labeling in the 11alpha-position, cortisol-13C(4),2H(1) used in this study served as an appropriate tracer for elucidating the kinetics of the interconversion of cortisol to cortisone in man.