Endocrine Abstracts

Intracellular cortisol is regulated by 11βHSD1. Although the field has focused on regeneration of cortisol from inert cortisone by 11β-reductase activity of 11βHSD1, we have used stable isotope tracers and arteriovenous sampling to quantify simultaneous dehydrogenase (cortisone generation) and reductase (cortisol regeneration) in human adipose and skeletal muscle. In vitro studies suggest insulin regulates this balance of reductase vs dehydrogenase acti...

Human plasma contains both cortisol (F) and corticosterone (B). B has been largely neglected in humans as it is 10–20 times less abundant however previous studies suggest B and F have differential tissue-specific actions. Compared with F, B has an enhanced response to ACTH, relatively higher concentrations in brain and CSF and differential transmembrane trafficking by ATP-binding cassette (ABC) transporters. Plasma F is bound to corticosteroid-binding globulin (CBG) and a...

Background: Using a deuterated tracer (D4-cortisol) to measure cortisol regeneration from cortisone in vivo we have quantified tissue-specific 11βHSD1 activity in health and disease, and acute regulation eg by insulin. These studies relied on tracer enrichment in the total plasma cortisol pool, assuming rapid equilibration between free and protein-bound pools. Slower equilibration would result in underestimation of enzyme activity, and has implications for the co...