Evidence That Corticotropin‐Releasing Hormone Acts as a Growth Hormone‐Releasing Factor in a Primitive Teleost, the European Eel ( Anguilla anguilla)

• Published in: Journal of Neuroendocrinology
• Main Authors: Rousseau, Le Belle, Marchelidon, Dufour
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1999
• Subjects: Anguilla anguilla; European eel
• Online Access: http://dx.doi.org/10.1046/j.1365-2826.1999.00334.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2826.1999.00334.x; https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2826.1999.00334.x; https://onlinelibrary.wiley.com/doi/full-xml/10.1046/j.1365-2826.1999.00334.x

The inhibitory control of growth hormone (GH) release by somatostatin (SRIH) has been conserved throughout vertebrate evolution. In contrast, the neuropeptides involved in the stimulatory control of GH vary according to species and/or physiological situations. We investigated the direct pituitary regulation of GH release in a primitive teleost, the European eel ( Anguilla anguilla L.) at the juvenile stage. Short‐term serum‐free primary cultures of dispersed pituitary cells were used, and GH release was measured by an homologous radioimmunoassay. Whereas growth hormone‐releasing hormone (GHRH), gonadotropin‐releasing hormone (GnRH), thyrotropin‐releasing hormone (TRH), neuropeptide Y (NPY) and cholecystokinin (CCK) failed to induce any change in GH release, corticotropin‐releasing hormone (CRH) dose‐dependently stimulated GH release with a significant effect at 1 nM and a maximal effect (≥400% of controls at 24 h) at 100 nM. In agreement with our previous studies, PACAP also stimulated GH release but its maximal effect was lower than that ofCRH. Proopiomelanocortin (POMC)‐peptides, corticotropin (ACTH), melanotropin ( α ‐MSH), β ‐endorphin) had no effect on GH release, at any dose tested (0.1–1000 nM), indicating that the stimulatory effect of CRH on GH release by somatotrophs was not mediated by CRH‐induced release of POMC‐peptides from corticotrophs and melanotrophs. The CRH antagonist, α ‐helical CRH(9–41), significantly inhibited the stimulatory effect of CRH on GH release, suggesting the implication of specific CRH receptors related to mammalian ones. The stimulatory effect of CRH on GH release was reduced after 24 h of incubation, indicating a desensitization. In contrast, no desensitization to the inhibitory effect of SRIH was observed. SRIH inhibited CRH action in a dose‐dependent manner. The effect of SRIH was overriding, 1 nM SRIH being able to abolish the effect of 1000 nM CRH. In conclusion, in the eel, CRH stimulates GH release directly at the pituitary cell level. GH and cortisol secretions could ...