An in vivo microdialysis coupled with liquid chromatography/tandem mass spectrometry study of cortisol metabolism in monkey adipose tissue

by Sun, L.; Stenken, J. A.; Brunner, J. E.; Michel, K. B.; Adelsberger, J. K.; Yang, A. Y.; Zhao, J. J.; Musson, D. G.

It is postulated that elevated tissue concentrations of cortisol may be associated with the development of metabolic syndrome, obesity, and type 2 diabetes. The 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1) enzyme regenerates cortisol from inactive cortisone in tissues such as liver and adipose. To better understand the Pivotal role of 11 beta-HSD1 in disease development, an in vivo rnicrodialysis assay coupled with liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis using stable isotope-labeled (SIL) Cortisone as a substrate was developed. This assay overcomes the limitations of existing methodologies that Suffer from radioactivity exposure and analytical assay sensitivity and specificity concerns. Analyte extraction efficiencies (E-d) were evaluated by retrodialysis. The conversion of SIL-cortisone to SIL-cortisol in rhesus monkey adipose tissue was studied. Solutions containing 100, 500, and 1000 ng/mL SIL-cortisone were locally delivered through an implanted 30-mm microdialysis probe in adipose tissue. At the delivery rate of 1.0 and 0.5 mu L/min, E-d values for SIL-cortisone were between 58.7 +/- 5.6% (n = 4) and 72.7 +/- 1.3% (n = 4), whereas at 0.3 mu L/min E-d reached nearly 100%. The presence of 11 beta-HSD1 activities in adipose tissue was demonstrated by production of SIL-cortisol during SIL-cortisone infusion. This methodology could be applied to cortisol metabolism studies in tissues of other mammalian species.

Analytical Biochemistry
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1096-0309; 0003-2697