HOME HELP CONTACT US SUBSCRIPTIONS ARCHIVE SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Accepted manuscript (PDF) All Versions of this Article: JOE-08-0410v1 200/1/117    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Geven, E. Articles by Klaren, P. Search for Related Content PubMed PubMed Citation Articles by Geven, E. Articles by Klaren, P.

E Geven, Animal Physiology, Radboud University Nijmegen, Nijmegen, Netherlands
G Flik, Animal Physiology, Radboud University Nijmegen, Nijmegen, Netherlands
P Klaren, Animal Physiology, Radboud University Nijmegen, Nijmegen, 6525 ED, Netherlands

Correspondence: Peter Klaren, Email: p.klaren{at}science.ru.nl

Abstract

In teleostean fishes the hypothalamo-pituitary-thyroid-axis (HPT-axis) and the hypothalamo-pituitary-interrenal-axis (HPI-axis) regulate the release of thyroid hormones and cortisol, respectively. Since many actions of both hormones involve regulation of metabolic processes, communication between both signal-pathways can be anticipated. In this study we describe central and peripheral sites for direct interaction between mediators of both neuro-endocrine axes in the common carp (Cyprinus carpio). Despite suggestions in the literature that corticotropin-releasing hormone (CRH) is thyrotropic in some fish, we were not able to establish stimulatory effects of CRH on the expression of the pituitary TSH-β subunit gene. In preoptic area tissue incubated with 10-7 M thyroxine (T4) a 2.9-fold increase in the expression of CRH-binding protein (CRH-BP) was observed. Thus T4 could reduce the bioavailable hypothalamic CRH via the up regulation of CRH-BP expression and hence down regulate the HPI-axis. At the peripheral level, cortisol (10-6 M), adrenocorticotropic hormone (ACTH, 10-7 M) and -melanocyte-stimulating hormone (-MSH, 10-7 M) stimulate the release of T4 from kidney and head kidney fragments, which contain all functional thyroid follicles in carp, by 2- to 4-fold. The substantiation of 3 pituitary thyrotropic factors, viz. TSH, ACTH and -MSH, in common carp, allows for an integration of central thyrotropic signals. Clearly, two sites for interaction between the HPT-axis, the HPI-axis and -MSH are present in common carp. These interactions may be key to proper regulation of general metabolism in this fish.