Cisbio's HTRF cortisol assay performed on the PHERAstar FS

Jean-Luc Tardieu, Francois Degorce Cisbio 03/2007

Cortisol is a corticosteroid hormone present in many metabolic processes, inducing key enzymes of carbohydrate, fat and protein metabolism. Cortisol acts anti-inflammatory and as an immunosuppressor. One way to create thehormone is by reduction of cortisone by 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta- HSD1).


The cortisol assay is a monoclonal antibody based competitive assay running in two steps. After the dehydrogenase reaction is finished (stimulation), anti-cortisol cryptate (donor) and d2 labeled cortisol (acceptor) are added to the reaction. The anti-cortisol cryptate and the d2 labeled cortisol will bind to each other leading to a high HTRF® signal. Cortisol built during the enzymatic reaction will compete with d2-labeled cortisol for the binding to the cryptate conjugate, resulting in signal loss (detection).


The PHERAstar® FS microplate reader in combination with the optimized HTRF® optical module provides outstanding sensitivity and accuracy. Moreover, the dual simultaneous measurement minimizes the read time for assays.

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