title: Stress responsiveness of the pituitary-interrenal axis during early life stages of common carp (Cyprinus carpio).
abstract: Whole-body levels of ACTH, alpha-MSH and cortisol in eggs and larvae of the common carp (Cyprinus carpio) were determined periodically up until 168 h after fertilisation. ACTH, alpha-MSH and cortisol immunoreactivity was detected in unfertilised eggs, and endogenous production of ACTH and alpha-MSH was observed 24 h after fertilisation and that of cortisol 36 h after fertilisation. ACTH immunoreactivity reached peak levels before hatching (56-72 h after fertilisation) and remained relatively stable thereafter, while alpha-MSH immunoreactivity started to increase after hatching. At 36 h after fertilisation, whole-body cortisol levels increased rapidly reaching peak levels at the end of hatching (72 h after fertilisation), remaining stable until the end of the experiment. From 50 h after fertilisation onwards, embryos and larvae increased their whole-body cortisol levels when subjected to handling (mechanical pressure during egg stage or netting during the larval stage). It is concluded that the pituitary-interrenal axis in carp is fully functional at the time of hatching. No indications of a stress non-responsive period after hatching were observed. To characterise ACTH and alpha-MSH immunoreactivities in carp larvae, whole-body homogenates were analysed by HPLC, with pituitary homogenates of adult carp serving as a reference. ACTH and alpha-MSH immunoreactivity in carp larvae homogenates consisted of three and two products respectively. HPLC of adult carp pituitaries revealed the presence of two ACTH immunoreactive products, which may represent a phosphorylated and a non-phosphorylated ACTH variant, while the three alpha-MSH peaks most likely represent des-acetylated, mono-acetylated and di-acetylated alpha-MSH, the latter being the predominant form. In carp larvae, however, one of the ACTH immunoreactive products co-eluted with the non-phosphorylated ACTH, while the two alpha-MSH products identified co-eluted with des-acetylated and mono-acetylated alpha-MSH, indicating that POMC processing at this stage of development is different from prohormone processing in adult fish.
authors.affiliation: Department of Animal Physiology, Faculty of Science, University of Nijmegen, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Stouthart
authors.forename: E C
authors.initials: EC
authors.lastname: Lucassen
authors.forename: F J
authors.initials: FJ
authors.lastname: van Strien
authors.forename: P H
authors.initials: PH
authors.lastname: Balm
authors.forename: R A
authors.initials: RA
authors.lastname: Lock
authors.forename: S E
authors.initials: SE
authors.lastname: Wendelaar Bonga
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D002347:Carps / Q000196:embryology*; D002851:Chromatography, High Pressure Liquid; D006854:Hydrocortisone / Q000032:analysis / Q000378:metabolism*; D007150:Immunohistochemistry; D007401:Interrenal Gland / Q000196:embryology* / Q000378:metabolism; D010902:Pituitary Gland / Q000196:embryology* / Q000378:metabolism; D011863:Radioimmunoassay; D018709:Statistics, Nonparametric; D013312:Stress, Physiological / Q000503:physiopathology*; D000521:alpha-MSH / Q000032:analysis / Q000378:metabolism
chemical_list: D000521:alpha-MSH; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone