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This Article Full Text Full Text (PDF) All Versions of this Article: 289/3/R814    most recent 00826.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (18) Citing Articles via Google Scholar Google Scholar Articles by Metz, J. R. Articles by Flik, G. Search for Related Content PubMed PubMed Citation Articles by Metz, J. R. Articles by Flik, G.

COMPARATIVE AND EVOLUTIONARY PHYSIOLOGY

ACTH, -MSH, and control of cortisol release: cloning, sequencing, and functional expression of the melanocortin-2 and melanocortin-5 receptor in Cyprinus carpio

Department Organismal Animal Physiology, Radboud University Nijmegen, Nijmegen, The Netherlands

Submitted 7 December 2004 ; accepted in final form 3 May 2005

Cortisol release from fish head kidney during the acute phase of the stress response is controlled by the adrenocorticotropic hormone (ACTH) from the pituitary pars distalis (PD). Alpha-melanocyte-stimulating hormone (-MSH) and -endorphin, from the pars intermedia (PI), have been implicated in cortisol release during the chronic phase. The present study addresses the regulation of cortisol release by ACTH and -MSH in common carp (Cyprinus carpio) and includes characterization of their receptors, namely, the melanocortin-2 and melanocortin-5 receptors (MC2R and MC5R). We could not demonstrate corticotropic activity of -MSH, -endorphin, and combinations of these. We do show a corticotrope in the PI, but its identity is as yet uncertain. Carp restrained for 1 and 7 days showed elevated plasma cortisol and -MSH levels; cortisol is still elevated but lower at day 7 than day 1 of restraint. Interrenal response capacity is unaffected, as estimated by stimulation with a maximum dose ACTH in a superfusion setup. MC2R and MC5R appear phylogenetically well conserved. MC2R is predominantly expressed in head kidney; a low abundance was found in spleen and kidney. MC5R is expressed in brain, pituitary PD, kidney, and skin. Quantitative PCR analysis of MC2R and MC5R expression in the head kidney of restrained fish reveals MC2R mRNA downregulation after 7 days restraint, in line with lower plasma cortisol levels seen. We discuss regulation of corticosteroid production from a phylogenetic perspective. We propose that increased levels of -MSH exert a positive feedback on hypothalamic corticotropin-releasing hormone release to sustain a mild stress axis activity.

receptor; stress