Microarray analysis of transcripts in the liver of gilthead sea bream with high plasma cortisol levels induced by slow-release cortisol implants

The present work was designed to assess the effects of high plasma cortisol levels induced by slow-release cortisol implants in the mRNA transcription of the GR in the different organs of the Sparus aurata, including liver. For that purpose fish were intraperitoneally injected with the implants containing two different concentrations of cortisol (50 or 200 µg/g body weight) and blood and organs were sampled after 7 and 14 days of implantation. Only fish with 200 µg/g implants exhibited a significant rise in the plasma cortisol. For microarray analysis we used livers of gilthead sea bream (N=36 fish). Fish were injected with 200 µg/g body weight of cortisol and sampled after 7 and 14 days (n=6 for each condition). RNA samples were grouped into pools of 2 animals for each time point. The analysis were carried out considering the transcripts differentially expressed in the group of fish implanted during 7 days with cortisol comparing to control group. Additionally, the transcripts differentially expressed at day 14 were compared with day 7.