Transcript levels of five enzymes involved in cortisol synthesis and regulation during the stress response in common carp: relationship with cortisol.

In this study the expression of five genes involved in cortisol synthesis and regulation in the head kidneys of common carp (Cyprinus carpio L.) has been investigated in response to 3h net confinement stress, followed by 22h recovery. Cortisol, glucose, lactate and free fatty acid levels were measured in blood plasma. StAR, P450c17a2, 3betaHSD, P450c21 and 11betaHSD2 transcript sequences were identified based on Cyprinidae homologs and quantified by real-time PCR. Results showed that the plasma cortisol level reached a peak at one hour post-stress (85-fold higher than in control) and quickly returned to normal after 4h recovery. 11betaHSD2 transcripts were for the first time identified in interrenals. Changes in cortisol levels during and after confinement were correlated in a time-delayed relationship with increase and decrease in mRNA levels of 11betaHSD2, respectively. These results suggest that cortisol may be involved in the control or activation of 11betaHSD2. StAR and P450c21 mRNA levels did not change during net confinement stress and recovery, but P450c17a2 levels were significantly increased 4 and 22h after recovery. Since plasma cortisol levels increased by 68-fold within 5min net confinement stress, it seems that transcriptional activation of this enzyme is not directly involved in acute cortisol production.