Evaluation of in vivo enzymatic activity of cortisol metabolism associated with hypertension

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This study is associated with a unique approach using stable isotope methodology in evaluating 11β-HSD2 activity in vivo based on urinary excretion of unconjugated (free) cortisol and cortisone. This stable isotope approach offered useful advantages since it allowed to measure stable isotopically labeled cortisol and its labeled metabolite cortisone the potential use of stable isotopically labeled cortisol in man as a tracer for the native cortisol to recognize the conversion of cortisol to cortisone in the kidney. Our results from the stable isotope methodology strongly suggest that the measurement of free cortisol and cortisone in urine is a significant advantage in assessing renal 1lb-HSD2 activity in man.The kidney is a major site for the conversion of cortisol to cortisone. Since the urinary free cortisone/ cortisol ratio has been proved to be a specific in vivo measure of 11β-HSD2 activity in human kidney reflecting intra-renal concentrations of cortisol and cortisone, a further study was performed to recognize the conversion of cortisol to cortisone catalized by 11β-HSD2 in patients with renal disease.This study provided direct evidence with regard to the usefulness of a urinary free cortisone/cortisol ratio as an index of human clinical tests for evaluating a reduced 11β-HSD2 activity.