title: Experimental hyperthyroidism and central mediators of stress axis and thyroid axis activity in common carp (Cyprinus carpio L.).
abstract: The effect of experimental hyperthyroidism, realized by T(4) injection, on central mediators of the hypothalamo-pituitary-interrenal axis (HPI-axis) in common carp (Cyprinus carpio L.) was studied. Our results show that hyperthyroidism evokes a marked 3.2-fold reduction in basal plasma cortisol levels. Corticotropin-releasing hormone-binding protein (CRH-BP) mRNA levels in the hypothalamus, measured by real-time quantitative PCR, were significantly elevated by 40%, but CRH, urotensin-I, prepro-TRH, prohormone convertase-1 (PC1), and POMC mRNA levels were unchanged. In the pituitary pars distalis, PC1, CRH receptor-1, and POMC mRNA levels were unaffected, as was ACTH content. Plasma alpha-MSH concentrations were significantly elevated by 30% in hyperthyroid fish, and this was reflected in PC1 and POMC mRNA levels in pituitary pars intermedia that were increased 1.5- and 2.4-fold respectively. The alpha-MSH content of the pars intermedia was unchanged. Hyperthyroidism has profound effects on the basal levels of a central mediator, i.e., CRH-BP, of HPI-axis function in unstressed carp in vivo, and we conclude that HPI- and hypothalamo-pituitary-thyroid-axis functions are strongly interrelated. We suggest that the changes in plasma cortisol, thyroid hormone, and alpha-MSH levels reflect their concerted actions on energy metabolism.
authors.affiliation: Department of Animal Physiology, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands.
authors.forename: Edwin J W
authors.initials: EJ
authors.lastname: Geven
authors.forename: Folkert
authors.initials: F
authors.lastname: Verkaar
authors.forename: Gert
authors.initials: G
authors.lastname: Flik
authors.forename: Peter H M
authors.initials: PH
authors.lastname: Klaren
mesh_terms: D000818:Animals; D002347:Carps / Q000378:metabolism*; D006728:Hormones / Q000097:blood; D006980:Hyperthyroidism / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism; D023421:Models, Animal; D012333:RNA, Messenger / Q000235:genetics; D013961:Thyroid Gland / Q000378:metabolism*
chemical_list: D006728:Hormones; D012333:RNA, Messenger