Differential expression of two glucocorticoid receptors in seabass (teleost fish) head kidney after exogeneous cortisol inoculation

Stressful conditions include a prompt release of corticosteroid hormones which can mediate gene expression through glucocorticoid receptors (GR). Since two seabass (Dicentrarchus labrax) GRs have been cloned and sequenced from peritoneal cavity cells (DIGR1) and liver (DIGR2), a comparative amino acid sequence analysis that included Haplochromis burtoni HbGRs, was carried out and homologies disclosed. The DIGR1 and DIGR2 deduced aminoacid sequences showed 61% identity (I) and 70% similarity (S). Moreover, DIGR2 was similar to HbGR2b (69% I, 73% S), and the DIGR1 to HbGR1 (72% I, 78% S). In addition, we examined the expression of the DIGRs after exogeneous cortisol inoculation into the peritoneal cavity, mimicking stress effects. At various times after the administration (3 h, 24 h, 1 week), gene expressions was evaluated in head kidney by real-time PCR. In addition, immunoblotting and densitometry analyses were performed with anti-DIGR1 antibodies. Although sea bass head kidney expressed both DIGR1 and DIGR2 they were differentially modulated by intraperitoneal implant of exogeneous cortisol. (C) 2010 Elsevier Inc. All rights reserved.